How many calories do you burn running? Roughly one kilocalorie per kilogram of body mass per kilometer traveled. If you weigh 70kg and run 5km, you burn approximately 350 calories. This is a baseline estimate; the actual number fluctuates based on your speed, efficiency, and the terrain.
Most fitness trackers provide a number that is a guess based on heart rate and a generic profile. Heart rate is a proxy for effort, not a direct measure of energy expenditure. To get a number that isn’t a hallucination, you have to look at METs.
The MET system
MET stands for Metabolic Equivalent of Task. One MET is the energy you expend sitting still—the baseline cost of existing. When you run, you operate at a multiple of that baseline.
Running is an expensive activity. Depending on your pace, running typically falls between 6 and 19 METs. A slow jog might be 6 METs (six times your resting energy spend), while a sprint is significantly higher.
The calculation is straightforward:
Calories = MET x weight (kg) x time (hours)
This is why weight matters. A 100kg runner spends more energy moving their mass over the same distance than a 60kg runner. Physics does not care about your goals; it only cares about mass and acceleration.
Why speed changes the number
The “1 kcal per kg per km” rule is a useful shorthand for general distance, but it ignores the metabolic cost of intensity. As you move faster, your running economy changes.
At very slow speeds, you are efficient. As you push toward your anaerobic threshold, the energy cost per kilometer increases. This is where the Compendium of Physical Activities becomes useful. It provides standardized MET values for specific speeds.
For example, running at 10 km/h has a different metabolic cost than running at 16 km/h. If you know your exact time and distance, you can match your speed to a MET value and get a number that is grounded in exercise science rather than a wrist-worn algorithm.
You can find a precise calculator for this at /tools/calories-burned.
The myth of the “fat burn zone”
There is a common belief that running slowly (Zone 2) burns a higher percentage of fat, while running fast burns carbohydrates. This is true on a percentage basis, but irrelevant for total energy balance.
If you run for 30 minutes at a low intensity, you might burn 300 calories, 60% of which come from fat. If you run for 30 minutes at a high intensity, you might burn 500 calories, 40% of which come from fat. In the second scenario, you burned more total fat (200 kcal vs 180 kcal) despite the lower percentage.
The most efficient way to burn calories is to move your mass over distance. The “zone” only matters if you are managing fatigue or training a specific energy system. If the goal is simply energy expenditure, the total work done is the only metric that matters.
The afterlife of the calorie
The most frustrating part of calorie counting is the “afterburn,” officially known as Excess Post-exercise Oxygen Consumption (EPOC). After a hard run, your body continues to burn calories at an elevated rate while it restores oxygen levels and repairs muscle tissue.
For a slow, solo jog, EPOC is negligible. For a high-intensity interval session, it is measurable. However, most people overestimate this effect. You cannot eat a celebratory cake and claim the “afterburn” will handle it. The math rarely supports that conclusion.
Frequently asked, quietly
Do I burn more calories running uphill? Yes. Gravity adds a vertical component to the work. Your body has to fight a constant force to move your mass upward, which increases the MET value of the activity.
Why does my watch say I burned 800 calories when the calculator says 500? Your watch is likely adding “basal metabolic rate” (BMR)—the calories you would have burned just by existing during that time—or it is overestimating based on a high heart rate.
Does running fasted burn more fat? It increases the percentage of fat oxidized during the run, but it does not significantly change the total calories burned. It mostly just makes you feel tired and irritable.
Are calories the best way to track progress? No. Calories are a measure of energy, not fitness. If you want to know if you’re getting better, look at your pace for the same effort or your VDOT.
If you want a number that isn’t a guess, put your weight and distance into the tool below.