How these numbers are calculated

This is the reference document that sits behind the Fueller calculator. It exists so every number the calculator gives a rider can be traced to a piece of sports nutrition literature. If a number isn't in §14, it doesn't ship. If §14 can't trace it to §15, it doesn't ship either.

Audience: a rider, coach, or curious sceptic who wants to audit how the calculator decides what to recommend. Tone is plain but technical where it needs to be.

1. Purpose & scope #

This tool is built for adult club cyclists on rides of roughly 1–4 hours, at paces between ~14 and ~22 mph. It assumes flat-to-rolling terrain, with optional cafe stops on longer days.

It is not built for:

• Under-18s (different energy and growth needs)
• Pregnancy or post-partum riding (please speak to your GP / midwife)
• Anyone with diabetes or an eating disorder history (please speak to your specialist)
• Ultra-distance (>6 hr) or stage racing (the recommendations top out)
• Professional racing (the modern peloton ingests 100–120 g/hr; that requires deliberate gut training and is not appropriate for amateur defaults¹¹)

It treats fuelling as four connected jobs: before, during, the cafe stop, and after.

2. The model in one paragraph #

The calculator asks for body weight, ride duration (computed from distance and pace), an intensity bucket, conditions, and an optional cafe-stop plan. From that it computes:

• kcal/hr for the ride (per intensity bucket, scaled to body weight; overridden by user-supplied watts when available)
• Carbs per hour using Jeukendrup's duration-graded ladder^{1, 2}
• Fluid per hour using a body-weight baseline with a heat multiplier, capped to protect against over-drinking^{3, 8}
• Sodium per hour as fluid × an assumed sweat-sodium concentration in the middle of the normal range⁹
• Pre-ride carbohydrate using Burke's 1–4 g/kg-in-1–4 hr framework⁴
• Recovery using a 1.0–1.2 g·kg⁻¹ CHO + ~0.3 g·kg⁻¹ protein target inside the first hour^{5, 6}
• Cafe stop as a planned refuel block sized to the remaining ride

Numbers default conservatively when the literature gives a range - easier to top up than to undo a GI blow-up or hyponatremia.

3. Energy: demand and supply #

Two questions sit underneath every number this calculator produces: how hard is the ride - the demand - and where does the body find the energy to meet it - the supply. The headline kcal figure answers the first. This section answers the second, because which fuel a rider burns is the whole reason carbohydrate timing matters at all. The infographic on the calculator's front page is a visual summary of §3.2–§3.7.

3.1 Energy demand - turning effort into calories

A cyclist's gross mechanical efficiency averages 20–25%, with population studies clustering around 22–24%^{10, 22}. The convenient shorthand is:

kcal/hr ≈ watts × 3.6

This is the formula used when a rider supplies expected average power. Without watts, the calculator uses pace + ride-type bucket as a proxy (see §14). Heart rate is deliberately not collected: an average HR for a ride - without that rider's own maximum and resting HR, and uncorrected for cardiac drift, heat, caffeine and fitness - cannot be tied to an energy or carbohydrate figure with any confidence, so asking for it would imply a precision the tool does not have.

Body weight scales the kcal estimate roughly linearly when watts are not provided - because at a given pace, a heavier rider does more total work (more rolling resistance, more elevation cost, similar aero overall). Power-based estimates already encode this, so when watts are supplied, weight scaling is skipped.

3.2 The two fuel tanks - fat and carbohydrate

The body meets that demand from two stores, and they could not be more different:

• Fat. Adipose tissue, plus a smaller store of fat inside the muscle itself. Even a lean rider carries 50,000+ kcal of it - enough for days of continuous riding. For any ride this calculator is built for, fat is effectively an unlimited tank^{4, 15}. The catch: fat oxidises slowly. It releases energy only fast enough to support low-to-moderate intensity, and cannot on its own fuel a hard pace.
• Carbohydrate. Stored as glycogen in the muscles (~300–500 g) and the liver (~80–110 g), plus a few grams of glucose circulating in the blood. Total: very roughly 500 g, about 2,000 kcal^{4, 15}. Small - but it is the fast fuel, the only one that can be broken down quickly enough to sustain tempo and threshold efforts.

That asymmetry is the entire point. The big tank is slow; the small tank is fast and runs out. Almost everything else in this document is about managing the small tank.

3.3 Intensity sets the fuel mix - the crossover concept

A rider is rarely burning purely one fuel; they burn a blend, and intensity sets the ratio. At an easy pace most of the energy comes from fat. As intensity climbs, the body shifts - "crosses over" - toward carbohydrate, because fat simply cannot be oxidised fast enough to keep up. Brooks & Mercier named this the crossover concept: as exercise gets harder, fat's contribution falls and carbohydrate's rises¹⁶. Fat oxidation peaks at a low-to-moderate intensity and tails toward zero at hard efforts.

Mapped onto the calculator's effort buckets (§14.1), the blend shifts roughly like this:

This is why the carbohydrate ladder (§14.2) nudges upward with intensity: a harder ride spends the small tank faster. The exact proportions vary with fitness and individual physiology, so the calculator treats this as a schematic, not a per-rider number.

3.4 Running the tank dry - "the bonk"

Depending on intensity, the ~2,000 kcal of stored carbohydrate typically lasts somewhere around 75 minutes at a hard threshold pace, up to 2–3 hours at an easy endurance one^{15, 17}. As muscle glycogen falls and the liver's store empties, blood glucose drops, and the rider is forced down to whatever pace fat alone can sustain. That sudden, unmistakable wall - heavy legs, no power, a foggy head - is what cyclists call the bonk (runners call it hitting the wall). It is not weakness; it is an empty fuel tank.

3.5 What carbohydrate during the ride actually does

You cannot make the small tank meaningfully bigger. What you can do is keep putting fuel into it. Carbohydrate eaten on the bike is digested into glucose, delivered to the bloodstream and the working muscles, and burned there. It keeps blood glucose up and carbohydrate oxidation high late in the ride - exactly when the internal store would otherwise be running out. In Coyle's classic feeding experiments, trained cyclists fed carbohydrate rode roughly an hour longer before fatiguing than the same riders on a placebo¹⁷.

That is the single reason the during-ride numbers exist. Pre-ride fuelling (§6) fills the tank before the start; on-bike carbohydrate (§4, §14.2) keeps it from emptying; recovery fuelling (§9) refills it afterwards.

3.6 Why fuelling well pays off

Fuelling is not only about avoiding the worst case. Getting it roughly right pays off in several ways the literature is consistent on:

• You hold your pace. Carbohydrate keeps power output and speed where the rider wants them and pushes back the onset of fatigue - the difference between finishing strong and crawling home (§3.5)^{17, 1}.
• Steadier blood sugar, fewer cravings. A blood-glucose crash (§3.4) is one of the body's oldest hunger signals: it brings on strong hunger and carbohydrate cravings, both on the bike and in the hours after it. Fuelling little and often keeps blood glucose stable, so the back half of the ride is not a fight with cravings.
• A clearer head. Carbohydrate has central-nervous-system effects, not only muscular ones^{1, 2}; conversely, low blood glucose dulls concentration, judgement and coordination - the "foggy head" of §3.4. On a bike, in traffic or on a fast descent, staying sharp is a safety matter, not only a comfort one.
• Better recovery, a better ride tomorrow. Carbohydrate taken during and after the ride starts refilling glycogen sooner, which means less next-day fatigue and a better second day for anyone riding back-to-back (§9)^{5, 6}.
• Avoiding the slow costs of under-fuelling. Habitually riding under-fuelled is the road to low energy availability - persistent fatigue, poor recovery, more frequent illness and low mood among its markers (§13)¹⁴. A single ride neither causes nor undoes this, but the habit is what counts.

None of this depends on hitting a number exactly. It mostly rewards simply not skipping food on any ride longer than an hour or so.

3.7 What about weight loss?

Riders often ask whether to use pacing or fuelling to lose weight, so it is worth answering plainly. The popular answer - the "fat-burning zone" - is largely a myth.

• Energy balance is what moves the needle. Loss of body fat comes from a sustained, modest energy deficit held over weeks; the higher the starting body-fat level the larger the deficit can reasonably be, and slower loss better preserves lean mass²⁰. Which fuel a rider oxidises during any single ride does not by itself determine fat loss - the body rebalances its fuel stores over the hours that follow.
• The "fat-burning zone". It is true that at a low intensity a greater proportion of energy comes from fat, and that whole-body fat oxidation peaks at a low-to-moderate intensity - roughly 50–65% of VO₂max - before falling away as intensity climbs¹⁸. But a larger share of a smaller total is not more fat lost. Higher-intensity riding burns more total energy per hour, and the week's energy balance, not the substrate split during one ride, is what counts (§3.3).
• Fasted and low-carbohydrate ("train low") riding. Training with low carbohydrate availability does raise fat oxidation during that session¹⁸ and drives some metabolic adaptation. But when total energy intake is matched, fasted or low-carbohydrate exercise has not been shown to produce greater fat loss than normally fuelled exercise¹⁹. "Train low" is a periodised tool for specific adaptations, not a weight-loss method; done habitually it lowers training quality and shades into the under-fuelling of §3.6 and §13.
• What the evidence supports. A modest deficit rather than a severe one (severe deficits cost muscle, recovery and hormonal health - §13¹⁴); enough protein to protect lean mass²⁰; fuelling the hard and long sessions properly while being lighter on short easy ones ("fuel for the work required", §6⁴); using easy-volume riding for sustainable, recoverable energy expenditure; and placing any weight-loss phase in the base season rather than alongside peak training.

The calculator stays out of this deliberately. Fueller's job (§1) is to fuel a given ride adequately; changing body composition is individual, easy to get wrong, and best worked through with a SENr-registered sports dietitian (§16). The eligibility note on the form already routes anyone with a history of disordered eating away from the tool entirely.

4. Carbohydrate intake during the ride #

The duration-graded recommendation from Jeukendrup^{1, 2} is now sport-nutrition orthodoxy:

Intensity nudges this upward at the margin. A short tempo ride is more glycogen-hungry than a longer social ride of equivalent duration, so the calculator allows a modest intensity bump at the top end (see §14).

Three important caveats for amateur riders:

• 90 g/hr is a ceiling for non-trained guts. The recent peloton-led move toward 100–120 g/hr is real and increasingly evidence-supported¹¹, but it requires weeks of "gut training" (progressive exposure) and is not suitable as an amateur default. I cap the recommendation at 90 g/hr and flag it as the high end of the normal range.
• CHO advice is in grams per hour, not per kilogram. Exogenous carbohydrate oxidation rates do not scale meaningfully with body weight¹. A 60 kg rider needs roughly the same g/hr as an 85 kg rider at equivalent intensity.
• Fructose is the tolerance-limiting ingredient. The glucose-plus-fructose mix is what lets total intake climb past ~60 g/hr, but fructose itself is the part an untrained gut struggles with - many riders are uncomfortable much above ~30 g/hr of fructose. Ramp the higher intakes up gradually across several rides rather than reaching straight for a 90 g/hr product.

5. Fluids and sodium #

The headline numbers are:

• Baseline fluid intake target: ~6–8 ml per kg body weight per hour. This is a practitioner heuristic rather than a figure lifted directly from a paper - it is consistent with the absolute during-exercise intake ranges in the ACSM fluid-replacement position stand³, which frames its guidance in litres per hour rather than per kilogram. For a 70 kg rider it works out to ~420–560 ml/hr.
• Heat uplift: in warm conditions (above ~20 °C) sweat rates rise; in hot conditions (above ~27 °C) endurance athletes commonly average ~1.2 L/hr with some hitting 3–4 L/hr⁸. The calculator applies a heat multiplier (§14).
• Hyponatremia cap: I cap the calculator's recommended fluid at 1 L/hr and surface a warning. Drinking beyond thirst is the primary mechanism of exercise-associated hyponatremia⁷. The Hew-Butler consensus is blunt: "the safest individualised hydration strategy before, during and immediately following exercise is to drink palatable fluids when thirsty."
• Sodium per litre of sweat varies hugely - roughly 230 to 1600 mg/L across most of the athlete population, with the saltiest sweaters exceeding 2,000 mg/L⁹. Without a sweat test I can't personalise this. The calculator defaults to ~600 mg/L (mid-range), which gives sensible totals for an average rider.

Practical translation: a rider on a warm-day 3-hour ride should expect to drink ~750 ml/hr containing around 450–500 mg sodium per hour. Most commercial isotonic mixes (SiS Go, Precision Hydration PH 500/1000, Veloforte) sit in this ballpark.

6. Pre-ride fuelling #

Burke's widely used framework⁴, which sits inside the broader sports-nutrition consensus tradition²¹, recommends a pre-ride carbohydrate dose of 1 to 4 g per kg body weight, eaten 1 to 4 hours before exercise, for any session lasting longer than about an hour.

The point is to top up liver glycogen so blood glucose holds during the ride. The longer the window, the larger and more solid the meal can be.

Low fat, low fibre, familiar. Race-day is not the day to try new foods.

The top of Burke's range - the full 3–4 g/kg - is built for long or hard events; for the 1–4 hr club rides this calculator covers, the lower-to-middle of each band is plenty. The calculator's pre-ride factors (§14.5) sit there deliberately: 2.5 g/kg for the long window, not 4.

Caffeine 3 mg/kg ~60 min before is ergogenic¹²; many riders already get this from a single mug of coffee.

7. During-ride food choices, UK-practical #

Real food works as well as branded products for most club rides. Approximate carbohydrate content of common cycling foods:

For 60 g/hr a rider can hit the target with one bottle of isotonic mix and one solid item, or two solid items and one bottle of water. The calculator surfaces concrete examples rather than just a number.

8. Cafe-stop framing #

Most longer club rides include a planned cafe stop. Treat this as a refuel point, not a treat to be earned. A 30-minute cafe stop sits inside the ride for fuelling purposes: the rider's glycogen is still depleting (slowly, while resting), and the cafe is an opportunity to take on more carbohydrate per minute than is comfortable on the bike.

Recommended cafe-stop carbohydrate (in addition to the on-bike average) for rides ≥2 hr with ~half the ride still to go:

Avoid fat-heavy options (full English, cheese sandwich, brownie) on rides with significant distance still to ride - they sit in the gut and slow re-engagement. They are fine post-ride.

9. Post-ride recovery #

The ISSN nutrient-timing position stand⁵ and a recent recovery review⁶ point the same way. The ISSN stand recommends aggressive carbohydrate refeeding (1.2 g·kg⁻¹·hr⁻¹), or carbohydrate at 0.8 g·kg⁻¹·hr⁻¹ combined with 0.2–0.4 g·kg⁻¹·hr⁻¹ of protein, in the hours after hard exercise. Distilling that into a single first-hour target, the calculator uses 1.0–1.2 g·kg⁻¹ CHO plus ~0.3 g·kg⁻¹ high-quality protein - a synthesis of those figures, not a verbatim quotation from either source.

For a 70 kg rider: ~80 g CHO and ~20 g protein. That's a chocolate milk (300 ml) + a banana + a slice of toast, or beans on toast + a yoghurt, or a recovery-mix shake + a banana.

When this really matters: back-to-back hard days, weekend rides where you're also riding Sunday, the day before a sportive. For a single ride a week, normal eating habits do the job and the 1-hour window is more flexibility than urgency.

Rehydration: drink 1.25–1.5× your sweat loss over the 2–4 hours after the ride³. Easiest measure: weigh yourself before and after. 1 kg lost ≈ 1 L of sweat; aim to drink 1.25–1.5 L back, with sodium (a salted meal works).

10. Caffeine #

Per the ISSN position stand¹²:

• Ergogenic dose: 3–6 mg per kg body weight, taken ~60 min pre-exercise. Doses above 9 mg/kg add side-effects without adding performance.
• Cap: 400 mg/day total intake (food + drink + supplements) is the FSA / NHS adult guideline.
• Timing: caffeine has a 4–6 hour half-life on average, but this varies widely between individuals - slow metabolisers can take 8+ hours to clear a dose. Avoid use after ~2 pm if sleep is sensitive, and earlier still if caffeine is known to keep you awake.
• Source: coffee, gels, tablets, energy drinks all work. Decaffeinated coffee is not a substitute.

A 70 kg rider taking 3 mg/kg gets ~210 mg - roughly one large filter coffee. The calculator surfaces this as an optional add-on, not a default.

11. Sex / gender considerations #

This is an area where the science is evolving fast and where popular discourse runs ahead of the evidence. Two positions to know:

• Sims' framework (Roar, podcasts, popular among female endurance athletes) argues that women have higher carbohydrate and protein needs than men relative to body weight, that the menstrual cycle phase materially changes fuelling needs, and that under-fuelling is the dominant practical risk for female endurance athletes.
• The methodological audit (Kuikman et al., "Fueling the Female Athlete"¹³) is sobering: of 197 studies on acute carbohydrate intake including women, only ~7% had adequate methodological control of ovarian hormones, and none met all best-practice recommendations. Frequent incorrect terminology and ~69% of studies failing to report menstrual status suggest the evidence base for cycle-specific recommendations is thin.

The protein side of the question is similarly unsettled. Some practitioners argue female athletes need more protein relative to body mass - particularly in the luteal phase - but, as with the carbohydrate claims, this is actively debated rather than established.

What the Fueller calculator does:

• Does not ask for sex/gender. Body weight already does the personalisation that the evidence supports, and asking for data it doesn't use would be misleading.
• Does not apply hidden multipliers based on sex.
• Does not ask about menstrual cycle phase. The evidence is not strong enough to justify it for amateur club riders, and asking is intrusive without a clear benefit.
• Does surface a general under-fuelling warning whenever the computed carbs-per-hour falls below the threshold for a long ride (§14.8) - under-fuelling is the dominant practical risk for all riders, especially female ones.

This is conservative on purpose. If a rider wants sex-specific or menstrual-cycle-aware fuelling they should work with a SENr-registered sports dietitian, not a quick calculator. The RED-S signposting in §13 and §16 stands as the catch-all flag.

12. Conditions: heat, cold, altitude #

Heat. Above ~20 °C, sweat rates rise; above ~27 °C they can double or triple⁸. The calculator's heat multiplier (§14) scales fluid and sodium together. It does not scale carbs - glycogen demand is largely intensity-driven, not temperature-driven.

Cold. It is easy to under-drink in cold weather. Thirst signal is blunted, and warm fluid in cold weather feels less appealing. The calculator nudges down only modestly in cool conditions (×0.85 fluid), and the in-app copy reminds riders to drink.

Altitude. Out of scope. Very few UK rides reach an altitude that matters physiologically. Riders on Alpine training camps should look elsewhere.

13. Special cases and red flags #

The calculator surfaces a "please ignore this and speak to a professional" chip in any of:

• Diabetes (insulin/CHO interaction is too individualised)
• Pregnancy or post-partum (out of scope)
• Eating-disorder history (BEAT helpline: 0808 801 0677)
• Body weight outside 40–130 kg (the model isn't calibrated)
• Ride duration >6 hr (ultra-distance is a different problem)

Under-fuelling is the most common practical mistake among club riders and the most consequential one. Symptoms include unexplained fatigue, poor recovery, frequent illness, low mood, missed periods, and stress fractures - collectively RED-S¹⁴. The 2023 IOC consensus update explicitly highlights "the emerging role of inadequate carbohydrate intake" as a driver of low energy availability, including in male athletes. If any of this rings true, speak to a SENr-registered sports dietitian; for non-clinical support, British Cycling's welfare team is also a route, and for an eating-disorder concern the BEAT helpline (0808 801 0677) is the dedicated UK service.

14. The calculator model - prose into numbers #

This is the section the calculator code consumes verbatim. Every number here traces to a citation in §15.

14.1 Ride-type buckets (reference rider: 75 kg)

Override rule: if the rider supplies expected average power, kcal/hr = watts × 3.6 and the bucket's kcal value is ignored. This overrides the energy estimate only - the effort-level bucket still sets the carbohydrate target (§14.2), so power does not replace it.

Bodyweight scaling for kcal (pace-based only): kcal_adjusted = kcal_default × (weightKg / 75). Skipped when watts are provided.

14.2 Carbs per hour

Cap: 90 g/hr. The 100–120 g/hr peloton range¹¹ is explicitly out of scope.
Floor warning: if computed < 30 g/hr on a ride >2 hr, surface an under-fuel chip.

Band edges are deliberate step changes, not smoothed. A ride that finishes near a boundary - 1 h 58 min, say - takes the value of whichever band it lands in, so the carb target can move sharply across a minute or two of duration. This is intentional: the bands mirror the way the source recommendations^{1, 2} are themselves stated as ranges, not a continuous curve. A rider near a boundary is best served by the conservative (higher) side - treat a near-2 hr ride as a 2–3 hr ride.

CHO is not scaled by body weight¹.

14.3 Fluid per hour

fluid_ml_per_hr = 7 × weightKg × heatMultiplier

Cap: 1000 ml/hr. Surfaces a chip referencing [7].

14.4 Sodium per hour

sodium_mg_per_hr = (fluid_ml_per_hr / 1000) × 600

The 600 mg/L assumed sweat sodium sits mid-range of the population⁹. A "salty sweater" can run past 3× this; a low sweater around a third. The calculator notes both endpoints in the disclaimer.

14.5 Pre-ride

pre_ride_CHO_g = weightKg × factor(hoursBefore)

Caffeine (optional, separate panel): caffeine_mg = weightKg × 3 (lower end of [12] range). Cap 400 mg/day.

14.6 Recovery

Within the first hour after the ride:

• recovery_CHO_g = weightKg × 1.0 ^{5, 6}
• recovery_protein_g = weightKg × 0.3 ^{5, 6}

Rehydration target: rehydration_ml = sweat_loss_L × 1375 (midpoint of 1.25–1.5×) ³.

For back-to-back-day riders, continue 1.0 g·kg⁻¹·hr⁻¹ CHO for 4 hours⁵. The calculator surfaces this as a note rather than a default schedule.

14.7 Cafe stop

If cafe_stop_enabled:

• cafe_CHO_g = round_to_5(remaining_hours × on_bike_CHO_per_hr × 0.75 + 10)
• Lower cap: 30 g (don't recommend zero)
• Upper cap: 120 g (don't recommend a feast)

The 0.75 multiplier plus 10 g front-load means a cafe stop delivers roughly three-quarters of the rider's remaining on-bike intake in one block, plus a small fixed top-up, letting them eat less aggressively on the back half of the ride. Sanity-check the resulting numbers land in the §8 bands:

Bias toward carb-forward orders for remaining_hours > 1.5; allow fat-heavier options when ≤1 hr remains.

14.8 Guardrails

• Weight clamp: 40 ≤ weightKg ≤ 130. Outside this, refuse to compute.
• Duration clamp: total ride hours > 6 - warn, still compute, flag "outside design".
• Fluid cap: 1000 ml/hr.
• Carb floor warning: <30 g/hr for ride >2 hr.
• Eligibility disclaimer: the form states up front that under-18s, pregnancy/post-partum, diabetes and eating-disorder history are out of scope and should see a GP / SENr dietitian. No medical data is collected.

14.9 Worked examples (must match the live calculator within rounding)

Example 1 - Social 90-min. 60 kg F, 20 mi @ 14 mph (≈1 h 26 min), mild, no cafe.

• Bucket = Social → kcal/hr = 400 × 60/75 = 320 kcal/hr → ~457 kcal total
• CHO/hr = 30 g (75–120 min Social - §14.2) → ~43 g total
• Fluid/hr = 7 × 60 × 1.00 = 420 ml/hr → ~600 ml total
• Sodium/hr = 250 mg/hr (420 ml × 0.6 g/L)
• Recovery = 60 g CHO + 18 g protein

Example 2 - Endurance 2 hr. 75 kg M, 32 mi @ 16 mph (2 h), mild.

• Bucket = Endurance → 550 × 75/75 = 550 kcal/hr → 1100 kcal total (75 kg is the reference rider, so the weight-scaling factor is ×1.00)
• CHO/hr = 60 g (durationHr exactly 2.0 lands in the 2–3 hr band, §14.2) → 120 g total
• Fluid/hr = 530 ml/hr (525 rounded to nearest 10) → 1060 ml total
• Sodium/hr = 320 mg/hr
• Recovery = 75 g CHO + 23 g protein

Example 3 - Big day + cafe. 80 kg M, 60 mi @ 20 mph (3 h), warm, cafe at mile 35 (mile 35 → 25 mi / 1 h 15 min remaining).

• Bucket = Tempo → 700 × 80/75 = 747 kcal/hr → 2241 kcal total
• CHO/hr = 60 g (2–3 hr boundary, §14.2) → 180 g on-bike total
• Fluid/hr = 7 × 80 × 1.25 = 700 ml/hr → 2100 ml total
• Sodium/hr = 420 mg/hr
• Cafe CHO = round_to_5(1.25 × 60 × 0.75 + 10) = 65 g (carb-forward)
• Recovery = 80 g CHO + 24 g protein

Example 4 - Short tempo. 70 kg M, 25 mi @ 21 mph (~1 h 11 min), cool.

• Bucket = Tempo (pace ≤21 mph is the tempo band, threshold begins above 21) → 700 × 70/75 = 653 kcal/hr → ~777 kcal total
• CHO/hr = 30 g (tempo, 30–75 min band per §14.2) → ~36 g total
• Fluid/hr = 7 × 70 × 0.85 = 416 → rounds to 420 ml/hr → ~500 ml total

Example 5 - Hot day. 65 kg F, 40 mi @ 17 mph (~2 h 21 min), hot.

• Bucket = Endurance → 550 × 65/75 = 477 kcal/hr → ~1120 kcal total
• CHO/hr = 60 g (>2 hr) → ~141 g total
• Fluid/hr = 7 × 65 × 1.50 = 682.5 → rounds to 680 ml/hr → ~1600 ml total. Under the 1000 ml/hr cap - no hyponatremia warning.
• Sodium/hr = 410 mg/hr

Example 6 - Silly input. 200 kg, 5 mph, 4 hr, hot.

• Weight outside clamp. Refuse to compute; signpost SENr dietitian.

15. Sources #

Numbers in [brackets] reference these. Evidence tier indicated where useful: T1 = peer-reviewed primary or consensus statement; T2 = practitioner-facing review; T3 = reputable summary.

1. Jeukendrup A. (2014). A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During Exercise. Sports Medicine 44(Suppl 1):S25–S33. T1. pmc.ncbi.nlm.nih.gov/articles/PMC4008807/
2. Jeukendrup A. (2008). Carbohydrate feeding during exercise. European Journal of Sport Science 8(2):77–86. T1. onlinelibrary.wiley.com/doi/10.1080/17461390801918971
3. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. (2007). American College of Sports Medicine Position Stand: Exercise and Fluid Replacement. Medicine & Science in Sports & Exercise 39(2):377–390. T1. pubmed.ncbi.nlm.nih.gov/17277604/
4. Burke LM, Hawley JA, Wong SHS, Jeukendrup AE. (2011). Carbohydrates for training and competition. Journal of Sports Sciences 29(Suppl 1):S17–S27. T1. tandfonline.com/doi/full/10.1080/02640414.2011.585473
5. Kerksick CM, Arent S, Schoenfeld BJ, et al. (2017). International society of sports nutrition position stand: nutrient timing. Journal of the International Society of Sports Nutrition 14:33. T1. pmc.ncbi.nlm.nih.gov/articles/PMC5596471/
6. Naderi A, Rothschild JA, Santos HO, et al. (2025). Nutritional Strategies to Improve Post-exercise Recovery and Subsequent Exercise Performance: A Narrative Review. Sports Medicine 55(7):1559–1577. T1. pmc.ncbi.nlm.nih.gov/articles/PMC12297025/
7. Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. (2015). Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. T1. Carlsbad 2015 consensus statement (PDF)
8. GSSI. Hydration and nutrition considerations for endurance cycling exercise in the heat. Sports Science Exchange. T2. gssiweb.org
9. Barnes KA, Anderson ML, Stofan JR, Dalrymple KJ, Reimel AJ, Roberts TJ, Randell RK, Ungaro CT, Baker LB. (2019). Normative data for sweating rate, sweat sodium concentration, and sweat sodium loss in athletes: An update and analysis by sport. Journal of Sports Sciences 37(20):2356–2366. T1. tandfonline.com/doi/full/10.1080/02640414.2019.1633159
10. CTS / Stages Cycling - Energy Expenditure: Calories, Kilojoules, and Power in Cycling. Practitioner summary of gross efficiency (~20–25%) and the watts × 3.6 conversion. T3. trainright.com
11. Wilson PB. (2026). A Narrative Review of the High-Carbohydrate Fueling Revolution (≥ 100 g/h) in the Professional Peloton. Sports Medicine 56(2):295–313. T1. pmc.ncbi.nlm.nih.gov/articles/PMC12982284/
12. Guest NS, VanDusseldorp TA, Nelson MT, et al. (2021). International society of sports nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition 18:1. T1. pubmed.ncbi.nlm.nih.gov/33388079/
13. Kuikman MA, Smith ES, McKay AKA, et al. (2023). Fueling the Female Athlete: Auditing Her Representation in Studies of Acute Carbohydrate Intake for Exercise. Medicine & Science in Sports & Exercise 55(3):569–580. T1. pmc.ncbi.nlm.nih.gov/articles/PMC9924969/
14. Mountjoy M, Ackerman KE, Bailey DM, et al. (2023). 2023 IOC consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine. T1. pubmed.ncbi.nlm.nih.gov/37752011/
15. Hearris MA, Hammond KM, Fell JM, Morton JP. (2018). Regulation of Muscle Glycogen Metabolism during Exercise: Implications for Endurance Performance and Training Adaptations. Nutrients 10(3):298. T1. pmc.ncbi.nlm.nih.gov/articles/PMC5872716/
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16. Disclaimer #

This tool is general guidance for healthy adult cyclists. It is not medical advice and is not a substitute for advice from a registered dietitian, GP, or coach. If you have diabetes, are pregnant, have a history of disordered eating, or are training at a level beyond club riding, please ignore this tool and work with a SENr-registered sports dietitian. Numbers are reference ranges - your sweat rate, sweat sodium, gut tolerance and energy demand are personal. Start conservative, test in training, never trial new fuel on race day.