How the calculation works
Every activity here carries a metabolic cost, expressed as a MET value. The calculation multiplies that cost by how heavy you are and how long you kept it up:
A 150-pound person walking slowly for 45 minutes burns roughly 108 calories. The same 45 minutes of running fast burns 657. The activity matters far more than the duration — you would need to walk slowly for over four and a half hours to match that run.
One detail worth knowing: the MET figures used here are not a single number per activity. They shift slightly across body weight, following published activity tables that report separate figures at 125, 155 and 185 pounds. Between those points the calculator interpolates; beyond them it holds the end value.
What a MET actually is
One MET is the energy your body uses sitting quietly — about 3.5 milliliters of oxygen per kilogram of body weight per minute. Everything else is expressed as a multiple of that. An activity at 4 METs costs four times what sitting still costs.
The convention was derived from one reference subject: a healthy 40-year-old man weighing 70 kg. That is worth remembering, because your own resting metabolism may sit meaningfully above or below that baseline depending on your lean mass, age and health.
Rough bands: under 3 METs is light (walking slowly, cooking, light housework), 3 to 6 is moderate (brisk walking, doubles tennis, gardening), and above 6 is vigorous (running, fast cycling, rope jumping). Public health guidance is usually written in these terms — 150 minutes a week of moderate activity, or 75 minutes of vigorous.
Why body weight changes the answer
Moving a heavier body over the same distance takes more work, so calories scale with weight. Two people doing the identical workout can differ by several hundred calories purely because one is larger.
This is also why the same run gets slightly cheaper as you lose weight, and why a plan built on a fixed daily burn drifts out of date. The second card above shows the same activity across a range of body weights so the size of that effect is visible rather than assumed.
Duration or distance: which to use
Use the duration mode for anything measured in time — a gym class, a swim, an hour of gardening. Use the distance mode when you know how far you went, which is the natural way to think about walking, running and cycling.
The two modes agree with each other. Distance mode simply works out how long the effort took at your pace, then applies the same MET arithmetic. Where they differ in feel is that distance mode also accounts for pace properly: covering five miles at a fast run costs more per mile than strolling the same five miles, because the intensity is higher, not just because the time is shorter.
The presets in distance mode correspond to the named speeds behind the calculation: for walking, 2.0, 2.8, 3.5 and 4.0 mph; for running, 5.0, 6.0, 7.5 and 10.0 mph; for cycling, 13, 15, 17.5 and 21 mph.
How accurate this is
Treat the result as a reasonable estimate with meaningful error bars, not a measurement. Several things push it around:
- MET values are population averages. They were measured on groups and describe a typical person, not you.
- Fitness cuts both ways. A fitter person is more efficient and burns slightly less doing the same task.
- The reference resting rate may not be yours. Studies have found the conventional 1 MET assumption overstates resting oxygen use by up to 20–30% in some people.
- Real activity is not constant. An hour of tennis includes standing around between points. Entering the full hour overstates the burn.
- Terrain, wind, altitude and temperature all move the number and none of them are inputs here.
Fitness trackers are not obviously better. They use heart rate and motion to estimate the same quantity and carry their own error, often substantial for calorie estimates specifically even when heart rate itself is accurate.
Calories burned and weight change
Weight change follows the balance between what you eat and what you spend, where spending is mostly your basal metabolic rate rather than exercise. For most people, exercise is a modest share of the daily total — which is why the burn figure above is smaller than people expect.
A useful sanity check: a single chocolate bar is roughly 250 calories, close to an hour of brisk walking for a 150-pound person. That is not an argument against exercising, which improves cardiovascular health, insulin sensitivity, mood and sleep regardless of what the scale does. It is an argument against treating exercise as a licence to eat back the estimate, especially since the estimate itself may be off by 20%.
If you want a full daily picture, the calorie calculator covers intake needs and the BMR calculator covers what you burn at rest.
What the number does not include
- Your resting burn. The figure is total energy for the activity, which includes what you would have spent anyway sitting still during that time.
- Afterburn. Elevated metabolism following hard exercise is real but modest, and is not counted here.
- Muscle gained. Resistance training changes body composition over months in ways a per-session calorie figure does not capture.
- Individual metabolism. Thyroid function, medication, sleep and genetics all shift the real number.
Frequently asked questions
How many calories does walking burn?
For a 150-pound person, slow walking burns 145 calories an hour and brisk walking 257. Weight matters a lot — a 200-pound person walking briskly burns 344 an hour.
How many calories does running burn?
A 150-pound person running at a moderate pace burns 718 calories an hour, and 876 running fast. Running is among the highest-burning activities per minute available without equipment.
What is a MET value?
A multiple of your resting energy use. One MET is sitting quietly; an activity rated 5 METs costs five times as much energy per minute. It lets very different activities be compared on one scale.
Is this calculator accurate?
It is a solid estimate built on published MET data, but individual results vary by 20% or more depending on fitness, efficiency, terrain and metabolism. Use it for comparison between activities rather than as an exact measurement.
How many calories do I burn in a day without exercising?
That is your basal metabolic rate plus the energy of ordinary daily movement, typically 1,300 to 2,000 calories for most adults. The BMR calculator estimates it from height, weight, age and sex.
How many calories should I burn to lose a pound?
The common rule of thumb is a deficit of about 3,500 calories per pound of fat, though real weight loss is messier because metabolism adapts as you lose. Sustainable deficits usually come more from intake than from exercise.
Does swimming burn more calories than running?
Usually less per minute at comparable effort, though vigorous lap swimming comes close to moderate running. Swimming's advantage is that it is low impact, so it is often sustainable for longer.
Why do calorie estimates differ between calculators and watches?
They use different MET tables, different weight adjustments and, in the case of watches, heart rate models with their own assumptions. Differences of 20% between sources for the same workout are normal.
This calculator is provided for general education and is not medical or dietary advice. Calorie burn figures are population-average estimates and should not be used to set precise intake targets. If you are managing a health condition, taking medication that affects metabolism, or planning a significant change to exercise or eating, speak to a doctor or a registered dietitian first. If thoughts about food, exercise or body weight are affecting your daily life, support is available — in the US, the National Alliance for Eating Disorders helpline is free and staffed by clinicians on 1-866-662-1235. Learn more about how we build these tools or read our privacy policy.