Calories Burned Calculator

How many calories your body burns during an activity depends on enough variables that no calculator can give you an exact figure. The results here run on standardised data collected from an average person, so treat them as an estimate. The method is set out below.

For how many calories to eat each day, see the calorie calculator. Weight change comes down to one subtraction: calories eaten, minus calories burned through activity, minus your basal metabolic rate. Land on zero and your weight holds. Negative and you lose, positive and you gain.

How the calculation works

Calories = MET x 3.5 x body weight / 200 per minute

where:

• MET is the metabolic equivalent of the activity, an index of how hard it is
• body weight is in kilograms
• 3.5 is the millilitres of oxygen per kilogram per minute a body uses at rest
• 200 converts oxygen consumption into calories

Walking slowly has a MET of 2.0. For a 70 kg person that is 2.0 x 3.5 x 70 / 200, which is 2.45 calories a minute. Over 45 minutes that comes to 110 calories, and you have to walk for well over an hour to work off a single chocolate bar.

What changes the number

Body mass

A bigger body burns more, at rest and in motion, because there is more of it to move and more tissue to supply. Someone at 200 pounds running a mile burns roughly twice what someone at 100 pounds burns over the same mile, with everything else equal. This is why the calculator asks for your weight before anything else.

Duration

Longer means more, though the relationship is not as clean as it is with weight, because intensity is bound up in it. Walking one mile in an hour and walking five miles in an hour are the same duration and nothing like the same effort.

Intensity

The harder the activity, the more you burn, and intensity can be measured several ways with varying precision.

Heart rate is the accessible one. A higher heart rate during an activity generally means more effort. It is also unreliable as a cross-person measure, since resting and maximum heart rates vary widely, and a fitter person will hold a lower heart rate through the same work than an unfit one.

Oxygen consumption is the precise one. Intensity and oxygen use rise together in a straight line, and oxygen consumption during an activity compared with consumption at rest describes the metabolic demand directly. Unlike heart rate, oxygen demand tracks closely with body mass, which is what makes a standard table possible at all.

What a MET actually is

MET stands for metabolic equivalent of task. Several definitions exist; this calculator uses the original, which is based on oxygen use relative to body mass.

One MET is the energy an average person spends sitting quietly, roughly 3.5 mL of oxygen per kilogram per minute. That baseline came from measuring one specific subject: a healthy 40-year-old man weighing 70 kg. An activity at 2 METs takes twice the energy of sitting still, one at 8 METs takes eight times, and so on.

Activities are usually sorted into light, moderate and vigorous. Walking slowly is light at 2.0 METs. Doubles tennis is moderate at 5.0. Skipping at 100 turns a minute is vigorous at 11.0. The Compendium of Physical Activities, which is where these values come from, catalogues hundreds of them.

One point about fuel is worth knowing if fat loss is the goal. Intensity changes which fuel the body reaches for. Lower intensities draw proportionally more from fat, so longer easy sessions burn a higher fraction of fat. As intensity climbs the body shifts towards carbohydrate. Protein contributes so little in most circumstances that it can be ignored. The catch is that total calories still decide the outcome, and a hard session burns more of everything even while burning a smaller share of fat.

The other factors

Age. Resting energy expenditure falls with age, largely because lean mass declines. Two people identical except in age will not burn the same, and the older one burns less.

Body composition. Muscle costs more to maintain than fat. Two people at the same height and weight will differ if one carries more muscle.

Temperature. People burn more in warmer conditions, because the body is not diverting energy into staying warm.

Fitness. Being fitter means burning fewer calories doing the same work, since a trained body is more efficient. Fitness makes you better at the activity and worse at burning calories doing it.

Diet. What you eat affects metabolic rate, and a slower metabolism burns less overall.

Sleep. Short sleep cuts the number two ways: you train less because you are tired, and metabolic rate itself drops.

Burning calories by distance

The second calculator answers a different question: not how long you moved, but how far. For walking, running and cycling, the energy cost is close to proportional to distance and body weight.

Calories = cost per kilogram per kilometre x body weight x distance

Walking works out near 0.62 calories per kilogram per kilometre, so a 70 kg person covering 5 km burns around 218 calories. At 4 km/h that walk takes an hour and a quarter.

The part that surprises people is that pace barely changes the total over a fixed distance. Walking 5 km slowly and walking 5 km briskly burn roughly the same, because the work of moving your mass that far is the same either way. What pace changes is time, and therefore how many kilometres you can fit into the hour you have. Running burns more per kilometre than walking, around 0.86, because of the airborne phase in every stride and the braking on every landing. Cycling is the cheapest by a wide margin, near 0.33, since the bicycle carries your weight and rolling is far more efficient than stepping.

How accurate is any of this?

The MET is the weak link. By convention 1 MET is about 1 calorie per kilogram of body weight per hour, or 3.5 mL of oxygen per kilogram per minute, and that convention rests on a single 40-year-old 70 kg man. Resting metabolic rate depends on lean body mass, age, health and more, so anyone whose RMR sits far from his gets a less accurate answer. Studies have found the conventional 1 MET value overestimates resting oxygen consumption by 20% to 30% on average.

The second problem is the assumption of constant effort. MET values assume the activity runs continuously at one rate. An hour of tennis includes changing ends, retrieving balls and standing around talking, so the hour of tennis you log is not an hour of tennis. Uneven activities push the estimate high, sometimes substantially.

Getting a genuinely accurate figure means a lab: maximum oxygen uptake, maximum heart rate, resting metabolic rate, all measured on you so you become your own reference. That is not worth doing for most people. MET-based estimates work better as an index of relative intensity than as a personal calorie count. They tell you reliably that a 10 MET activity is twice as hard as a 5 MET one, and only approximately what either costs you.

Using the numbers without being fooled by them

Exercise is a smaller lever on weight than most people assume. An hour of moderate cycling for a 70 kg person burns roughly 590 calories, which a muffin and a large latte put straight back. Diet moves the total further with less effort, and the well-documented reason exercise disappoints on the scale is compensation: appetite rises, and unconscious daily movement falls after a hard session.

Track trends rather than single sessions. Watch fitness devices with some scepticism too, since wrist trackers estimate calorie burn from heart rate and motion, and validation studies routinely find errors of 20% to 90% on energy expenditure even where heart rate itself is accurate.

What these numbers do well is comparison. If you want to know whether swimming or cycling is the better use of forty minutes, or what a hilly walk is worth against a flat one, the MET table answers it clearly. Treat the calorie figure as a ranking rather than a budget.