How Many Calories Does a Marathon Burn? (And How Much You Need to Eat)
A marathon burns about 1 kcal per kg of body weight per kilometer: roughly 2,500 kcal for a 60 kg runner and 3,400 kcal at 80 kg. Here is the table by body weight, why pace barely changes it, why it leads to the wall, and what it means for eating before, during, and after the race.
Quick answer
Running a marathon burns about 1 kcal per kg of body weight per kilometer, so roughly 2,110 kcal for a 50 kg runner, 2,530 kcal at 60 kg, 2,950 kcal at 70 kg, 3,380 kcal at 80 kg, and 3,800 kcal at 90 kg. A half marathon burns about half of that. Pace changes the total very little because the cost per kilometer is similar at normal running speeds; body weight changes it a lot. You cannot replace it during the race. Eat 30 to 60 g of carbohydrate per hour, up to 90 g if gut-trained, start with full glycogen stores, and refuel with carbs and protein afterwards.
Running a marathon burns about 1 kcal for every kilogram of body weight for every kilometer. For a 70 kg (154 lb) runner that is roughly 2,950 kcal over 42.2 km, more than a full day of normal food. Pace changes the number less than most people think. Body weight changes it a lot.
This guide shows the numbers by body weight, explains where the energy comes from and why that leads to the wall, and turns it into what you should eat before, during, and after the race.
Marathon Calories by Body Weight
The rule of thumb comes from measurements of the energy cost of running, which is close to 1 kcal per kg per km across normal running speeds. Running economy differs between runners, so treat these numbers as good estimates, not exact values.
| Body weight | Half marathon (21.1 km) | Marathon (42.2 km) |
|---|---|---|
| 50 kg (110 lb) | About 1,050 kcal | About 2,110 kcal |
| 60 kg (132 lb) | About 1,270 kcal | About 2,530 kcal |
| 70 kg (154 lb) | About 1,480 kcal | About 2,950 kcal |
| 80 kg (176 lb) | About 1,690 kcal | About 3,380 kcal |
| 90 kg (198 lb) | About 1,900 kcal | About 3,800 kcal |
| 100 kg (220 lb) | About 2,110 kcal | About 4,220 kcal |
Real races match this well. In a study of recreational marathon runners, men burned about 2,800 kcal and women about 2,400 kcal for the full distance. Larger runners burned more, and ran slower, than smaller runners.
These are total numbers. They include the energy you would have used anyway just being alive, about 1 kcal per kg per hour. For a 70 kg runner finishing in four hours, that is roughly 280 kcal, so the extra cost of the race itself is closer to 2,650 kcal.
Does Pace Change It?
Less than you would expect. Per kilometer, running costs about the same energy whether you run fast or slow. A faster runner burns more calories per hour but for fewer hours, so the total for the distance comes out about the same.
| 70 kg runner finishing in | Calories per hour | Total for the marathon |
|---|---|---|
| 3:00 | About 985 kcal | About 2,950 kcal |
| 4:00 | About 740 kcal | About 2,950 kcal |
| 5:00 | About 590 kcal | About 2,950 kcal |
| 6:00 | About 490 kcal | About 2,950 kcal |
What pace does change is the fuel mix. The harder you run compared with your fitness, the more of the energy comes from carbohydrate instead of fat. At a hard, sustained effort most of it comes from carbohydrate. Slower runners burn a bit more fat, but they are on the course for longer, so they still use a lot of carbohydrate in total.
Why This Leads to the Wall
Your muscles and liver store carbohydrate as glycogen, but only a limited amount, roughly a few hundred grams depending on your size and how well you have loaded. At marathon pace a large share of the energy comes from carbohydrate, so a runner who does not eat during the race can run low somewhere in the last third. That is the wall: the pace drops, the legs feel heavy, and thinking gets foggy. Modeling studies estimate that more than two in five marathon runners hit it.
Two things push the wall back or remove it: starting with full glycogen stores and eating carbohydrate during the race. You are not trying to replace every calorie. You only need to keep enough carbohydrate coming in to hold your pace.
How Much to Eat During the Marathon
You cannot replace 3,000 kcal on the run. Your gut absorbs about 60 g of glucose per hour, or up to about 90 g when you mix glucose and fructose. That is 240 to 360 kcal per hour, a fraction of what you burn, and it is enough.
| Finish time | Carbs per hour | Calories from race fuel | Share of what a 70 kg runner burns |
|---|---|---|---|
| 3:00 | 60 to 90 g | 720 to 1,080 kcal | About 25 to 35 percent |
| 4:00 | 45 to 75 g | 720 to 1,200 kcal | About 25 to 40 percent |
| 5:00 | 40 to 60 g | 800 to 1,200 kcal | About 25 to 40 percent |
The rest comes from glycogen and fat. That split is why these amounts are enough to hold pace for most runners who start with full stores. Above 60 g per hour, use glucose-fructose products and only amounts you have practiced. The gel guide linked below turns this into a packet count.
How Much to Eat the Days Before
Carb loading does not mean eating 3,000 extra calories. It means making carbohydrate the biggest part of your food for 36 to 48 hours, about 8 to 10 g per kg of body weight per day, while training is light. For a 70 kg runner that is 560 to 700 g of carbohydrate, about 2,250 to 2,800 kcal from carbs alone. Total calories go up a little, carbs go up a lot, and fat and fiber come down.
How Much to Eat After the Marathon
You finish with a big energy gap and low glycogen stores. You do not need to eat it all back at once. In the first hour, aim for about 1 to 1.2 g of carbohydrate per kg plus 20 to 30 g of protein, and add more carbohydrate every couple of hours if you can. Over the next two days, eat to appetite with plenty of carbohydrate and protein. Hunger often comes back strongly the day after the race.
Will You Lose Weight Running a Marathon?
On race day you may be 1 to 3 kg lighter on the scale, but almost all of that is water and glycogen. It comes back within a day or two as you eat and drink. The whole race is worth about the energy stored in 0.4 kg of body fat, and only part of the energy actually comes from fat.
Training is different. Sixteen to twenty weeks of marathon training burn a lot of energy, and runners who under-eat in that block are the ones who get injured or sick. If you want to lose weight, do it slowly and far from race week. The weight loss guide linked below explains how.
Why Your Watch Shows a Different Number
Garmin, Apple Watch, and Strava estimate calories from heart rate, pace, and your profile. Lab studies find their calorie numbers are often 20 to 40 percent off for a single workout, even when heart rate is accurate, and some show only active calories. Use the 1 kcal per kg per km rule as a cross-check. If your watch is far away from it, trust the formula.
Enter your weight, goal pace, gel, and the weather. See how many carbs to eat per hour, how many gels to carry, how much to drink, and your pre-race carb target, in about a minute.
Frequently Asked Questions
How many calories does a marathon burn?
About 1 kcal per kg of body weight per km: roughly 2,530 kcal for a 60 kg runner, 2,950 kcal at 70 kg, and 3,380 kcal at 80 kg. Pace changes the total very little; body weight changes it a lot.
How many calories does a half marathon burn?
About half of a marathon: roughly 1,270 kcal at 60 kg, 1,480 kcal at 70 kg, and 1,690 kcal at 80 kg.
How many calories should I eat during a marathon?
Think in carbs, not calories: 30 to 60 g of carbohydrate per hour for most runners, up to 90 g per hour if you have trained your gut. That is 120 to 360 kcal per hour, much less than you burn, and enough to prevent the wall for most runners.
Do faster runners burn more calories in a marathon?
Per hour, yes. For the whole race, not really. The energy cost per kilometer is about the same across normal running speeds, so a faster runner burns more per hour for fewer hours.
How many calories should I eat after a marathon?
There is no need to replace everything at once. Eat 1 to 1.2 g of carbohydrate per kg plus 20 to 30 g of protein in the first hour, then normal meals with plenty of carbs and protein, eating to appetite for the next two days.
Is my watch calorie number for a marathon accurate?
It is an estimate. Lab studies find watch calorie numbers are often 20 to 40 percent off for a single workout. The 1 kcal per kg per km rule is a good cross-check.
Sources
Sources and official references
- 1.Energy Cost of RunningJournal of Applied Physiology (Margaria et al., 1963) · The energy cost of running per kilometer is about 1 kcal per kg and largely independent of speed
- 2.Energy Expenditure and Influence of Physiologic Factors During Marathon RunningJournal of Strength and Conditioning Research (Loftin et al., 2007) · About 2,800 kcal (men) and 2,400 kcal (women) for the marathon in recreational runners
- 3.Regulation of Endogenous Fat and Carbohydrate Metabolism in Relation to Exercise Intensity and DurationAmerican Journal of Physiology (Romijn et al., 1993) · Carbohydrate supplies a growing share of energy as exercise intensity rises
- 4.Metabolic Factors Limiting Performance in Marathon RunnersPLOS Computational Biology (Rapoport, 2010) · More than two fifths of marathon runners experience performance-limiting glycogen depletion
- 5.Skeletal Muscle Glycogen Content at Rest and During Endurance Exercise in Humans: A Meta-AnalysisSports Medicine (Areta and Hopkins, 2018) · High carbohydrate intake raises resting glycogen; intensity and starting glycogen drive how fast it is used
- 6.A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During ExerciseSports Medicine (Jeukendrup, 2014) · About 60 g per hour from glucose, up to 90 g per hour from glucose and fructose
- 7.International Society of Sports Nutrition Position Stand: Nutrient TimingJournal of the International Society of Sports Nutrition (Kerksick et al., 2017) · Post-exercise carbohydrate of about 1 to 1.2 g/kg per hour with protein for recovery
Prompt ideas for AI assistants
- “How many calories will I burn running a marathon at 64 kg in 4:15?”
- “How many gels do I need to cover my marathon if I weigh 78 kg?”
- “How much should I eat the day after a marathon?”
Mavr turns your weight and goal time into a marathon fuel plan: carbs per hour, gels to carry, fluids, and sodium, plus how much to eat in the days before and after.
Written by
Mavr Sports Nutrition Team
The Mavr sports-nutrition team translates peer-reviewed endurance research (Jeukendrup, Burke, the ISSN) into daily fueling for runners and triathletes.