Mavr Sports Nutrition Team
September 2, 2026. 13 min read.
Almost every runner has stood in a kitchen after a long run doing the same arithmetic: the watch says 940 calories, so what does that buy? The number matters, because eating far under it wrecks recovery and eating far over it quietly undoes a body-composition goal. The problem is that the number on your wrist is one of the least accurate things your watch reports, and the rule of thumb it is competing with is both simpler and, for most runners, closer to the truth.
This guide gives you the arithmetic, the charts, the correction factors that actually change the answer, and the research on how far off consumer devices are. Then it does the part most calculators skip: turning an energy number into what to eat.
The energy cost of running has been measured in laboratories for the better part of a century, and it collapses to something you can do in your head. Running costs approximately 1 kilocalorie for every kilogram of body mass you move over every kilometre of ground. In imperial units that is roughly 0.72 kilocalories per pound per mile.
The surprising part is what is missing from the formula: pace. Within the range most people run, the total energy needed to cover a fixed distance changes only modestly with speed. Running a 10K in 45 minutes and running the same 10K in 60 minutes cost roughly the same total energy, because you are moving the same mass the same distance. Faster running burns more calories per minute, not dramatically more per kilometre. Walking is the genuine exception, because walking is mechanically cheaper per unit distance than running until you approach a very brisk pace.
These are gross estimates on flat ground at a steady effort, calculated from the 1 kcal/kg/km relationship and rounded. Find the row closest to your body weight.
| Body weight | Per mile | 5K | 10K | Half marathon | Marathon |
|---|---|---|---|---|---|
| 50 kg / 110 lb | 80 kcal | 250 kcal | 500 kcal | 1,055 kcal | 2,110 kcal |
| 60 kg / 132 lb | 97 kcal | 300 kcal | 600 kcal | 1,266 kcal | 2,532 kcal |
| 70 kg / 154 lb | 113 kcal | 350 kcal | 700 kcal | 1,477 kcal | 2,954 kcal |
| 80 kg / 176 lb | 129 kcal | 400 kcal | 800 kcal | 1,688 kcal | 3,376 kcal |
| 90 kg / 198 lb | 145 kcal | 450 kcal | 900 kcal | 1,899 kcal | 3,798 kcal |
| 100 kg / 220 lb | 161 kcal | 500 kcal | 1,000 kcal | 2,110 kcal | 4,220 kcal |
Two things fall out of that table immediately. A marathon costs a normal-sized runner roughly a full day of maintenance energy, which is why the day after a marathon is not the day to diet. And a 5K, for all the effort it takes, costs about the same as one large bagel with peanut butter. Runners routinely overestimate what short hard sessions buy them and underestimate what long easy sessions demand.
Every number above is gross energy expenditure: the total your body used during the run, including the energy it would have spent sitting on the couch for the same period. If your goal is body composition, the honest figure is net: the extra energy the run cost you.
Resting metabolism runs at roughly 1 kcal per kilogram of body weight per hour. So a 70 kg runner sitting still for an hour spends about 70 kcal anyway. A one-hour run showing 700 gross kcal delivered about 630 kcal of extra expenditure. For a single run the difference is small. Across a 60-kilometre week it is a few hundred calories, and that is exactly the size of the error that makes a deficit stall or a gain creep.
30 min easy, 5 km
Gross (70 kg runner)350 kcal
Approx. net~315 kcal
Practical readA normal snack, not a licence for dessert
60 min steady, 10 km
Gross (70 kg runner)700 kcal
Approx. net~630 kcal
Practical readA real meal is warranted
2 h long run, 20 km
Gross (70 kg runner)1,400 kcal
Approx. net~1,260 kcal
Practical readNeeds fuel during, not just after
3.5 h marathon
Gross (70 kg runner)2,950 kcal
Approx. net~2,700 kcal
Practical readCannot be replaced in one sitting
| Session | Gross (70 kg runner) | Approx. net | Practical read |
|---|---|---|---|
| 30 min easy, 5 km | 350 kcal | ~315 kcal | A normal snack, not a licence for dessert |
| 60 min steady, 10 km | 700 kcal | ~630 kcal | A real meal is warranted |
| 2 h long run, 20 km | 1,400 kcal | ~1,260 kcal | Needs fuel during, not just after |
| 3.5 h marathon | 2,950 kcal | ~2,700 kcal | Cannot be replaced in one sitting |
Pace barely moves the total. These things genuinely do, and they are the corrections worth applying.
Uphill running
Effect on energy costSubstantially higher; climbing costs extra work against gravity
How to adjustAdd roughly 10 percent per 1 percent of average grade
Downhill running
Effect on energy costSlightly lower energy, much higher muscle damage
How to adjustDo not reduce recovery food because the calorie count dipped
Soft ground, sand, snow, trail
Effect on energy costHigher, sometimes far higher
How to adjustTreat a trail hour as a road hour plus 10 to 30 percent
Treadmill at 0 percent
Effect on energy costSlightly lower than outdoors, no air resistance
How to adjustSet 1 percent grade to approximate outdoor cost
Heat and humidity
Effect on energy costHigher at the same pace
How to adjustExpect a higher heart rate at unchanged energy demand
Carrying a pack or vest
Effect on energy costHigher in direct proportion to added mass
How to adjustAdd pack weight to body weight in the formula
Wind
Effect on energy costHigher into a headwind, small gain with a tailwind
How to adjustThe penalty exceeds the benefit on an out-and-back
| Factor | Effect on energy cost | How to adjust |
|---|---|---|
| Uphill running | Substantially higher; climbing costs extra work against gravity | Add roughly 10 percent per 1 percent of average grade |
| Downhill running | Slightly lower energy, much higher muscle damage | Do not reduce recovery food because the calorie count dipped |
| Soft ground, sand, snow, trail | Higher, sometimes far higher | Treat a trail hour as a road hour plus 10 to 30 percent |
| Treadmill at 0 percent | Slightly lower than outdoors, no air resistance | Set 1 percent grade to approximate outdoor cost |
| Heat and humidity | Higher at the same pace | Expect a higher heart rate at unchanged energy demand |
| Carrying a pack or vest | Higher in direct proportion to added mass | Add pack weight to body weight in the formula |
| Wind | Higher into a headwind, small gain with a tailwind | The penalty exceeds the benefit on an out-and-back |
Wrist-worn devices estimate energy expenditure from heart rate, motion, and your entered profile. Heart rate is a proxy for effort, not for energy, and it drifts with heat, dehydration, caffeine, stress, and sleep. Stanford researchers tested seven consumer wearables against clinical indirect calorimetry and found that none produced acceptable energy-expenditure accuracy: the best device had a median error rate of about 27 percent, and the worst exceeded 90 percent. Heart-rate measurement itself was good. The calorie conversion was not.
A 27 percent error on a 700 kcal run is nearly 200 kcal in either direction, every single run. That is why a runner who eats back exactly what the watch says can gain weight for months while doing everything the screen told them.
The practical policy: use the distance-based estimate for planning how much to eat, and use your watch for comparing today against last Tuesday. Do not use the watch number as a budget.
Here is the part almost no calories-burned-running calculator will tell you. Energy is not the limiting factor in a hard run. Carbohydrate is. Your body stores tens of thousands of calories as fat and only about 1,500 to 2,000 kcal as muscle and liver glycogen, and it is the glycogen that runs out at mile 20.
So the useful decomposition of a run is not "I burned 1,400 calories". It is "I used roughly 200 to 250 grams of carbohydrate, of which I replaced 60 during the run, so I am 150 grams short and I have a quality session tomorrow morning." That is an actionable sentence. The calorie total is not.
45 min easy
Approx. energy500 kcal
Approx. carbohydrate used40 to 60 g
What to replace firstNormal next meal is enough
75 min moderate
Approx. energy875 kcal
Approx. carbohydrate used90 to 130 g
What to replace firstCarbohydrate plus 20 to 30 g protein within a couple of hours
2 h long run
Approx. energy1,400 kcal
Approx. carbohydrate used150 to 220 g
What to replace firstFuel during the run; then carbs plus protein
2 h with intervals
Approx. energy1,500 kcal
Approx. carbohydrate used200 to 280 g
What to replace firstAggressive carbohydrate replacement if training again inside 24 hours
| Run | Approx. energy | Approx. carbohydrate used | What to replace first |
|---|---|---|---|
| 45 min easy | 500 kcal | 40 to 60 g | Normal next meal is enough |
| 75 min moderate | 875 kcal | 90 to 130 g | Carbohydrate plus 20 to 30 g protein within a couple of hours |
| 2 h long run | 1,400 kcal | 150 to 220 g | Fuel during the run; then carbs plus protein |
| 2 h with intervals | 1,500 kcal | 200 to 280 g | Aggressive carbohydrate replacement if training again inside 24 hours |
The proportion of fuel that comes from carbohydrate rises steeply with intensity. An easy jog runs largely on fat. A threshold session runs mostly on carbohydrate. Two runs that show an identical calorie total on your watch can leave you in completely different states.
This is where the number becomes a decision, and the answer depends on what you are training for.
Performance in a build block
How much of the run to replaceEffectively all of it
WhyUnder-fuelling in a build block is the fastest route to stalled adaptation and injury
Gradual fat loss while training
How much of the run to replaceMost of it; hold a small daily deficit, not a per-run one
WhyDeficits taken out of training days damage the sessions that matter
Race week
How much of the run to replaceAll of it, plus a deliberate carbohydrate top-up
WhyThe goal is full glycogen, not a tidy ledger
Easy or rest days
How much of the run to replaceEat less carbohydrate, hold protein steady
WhyCarbohydrate need moves with training; protein need does not
| Goal | How much of the run to replace | Why |
|---|---|---|
| Performance in a build block | Effectively all of it | Under-fuelling in a build block is the fastest route to stalled adaptation and injury |
| Gradual fat loss while training | Most of it; hold a small daily deficit, not a per-run one | Deficits taken out of training days damage the sessions that matter |
| Race week | All of it, plus a deliberate carbohydrate top-up | The goal is full glycogen, not a tidy ledger |
| Easy or rest days | Eat less carbohydrate, hold protein steady | Carbohydrate need moves with training; protein need does not |
The pattern that works is to move carbohydrate around your training rather than shrinking everything uniformly. That is also the pattern almost nobody executes by hand, because it means recalculating every day against a session that keeps changing.
Roughly 0.72 kcal per pound of body weight per mile. A 150 lb runner burns about 108 kcal per mile, a 200 lb runner about 144 kcal. Pace changes this far less than most people expect.
About 350 kcal for a 70 kg (154 lb) runner, scaling directly with body weight: roughly 250 kcal at 50 kg and 500 kcal at 100 kg. That is gross energy, so the extra cost above resting is about 10 percent lower.
Roughly 2,600 to 3,400 kcal for most runners, close to body weight in kg multiplied by 42. It is approximately a full day of maintenance energy on top of your normal day, which is why marathon recovery takes days of eating, not one large meal.
Per minute, yes. Per mile, only slightly. Covering the same distance faster burns marginally more total energy but takes less time, so the totals end up close. Faster running does shift the fuel mix strongly toward carbohydrate.
Wrist devices infer energy from heart rate, which rises with heat, dehydration, caffeine, and fatigue independently of energy cost. Independent testing has found median energy-expenditure errors above 27 percent even for the best consumer devices. Use the watch to compare your own runs, not to set a food budget.
In a training block, yes, essentially all of them. If you are losing weight, hold a small deficit across the week rather than taking it out of the days you train hardest, and never take it out of race week.
General guidance for healthy adults, not medical advice. Talk to a doctor or registered dietitian if you have a health condition, take medicines or have special dietary needs. Caffeine advice is for healthy adults only. EFSA's safe limit is 200 mg in one dose and 400 mg in a day.
Mavr converts each run into carbohydrate, protein, and calorie targets for the rest of the day, so the burn number becomes a meal plan rather than trivia.
Ask Kai, the coach in the app