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What a MET is and where the numbers come from

A metabolic equivalent of task is a ratio. One MET is defined as the energy cost of sitting quietly, conventionally 3.5 millilitres of oxygen consumed per kilogram of body mass per minute, which works out at about one kilocalorie per kilogram per hour. An activity rated at 8 METs therefore costs roughly eight times what sitting costs. The unit exists because it makes activities comparable across people of very different sizes without quoting a separate calorie figure for each one.

The MET values themselves are not guesses. They come from the Compendium of Physical Activities, first published by Barbara Ainsworth and colleagues in 1993 and updated in 2000, 2011 and again in 2024. Each entry carries a five-digit code, a description precise enough to distinguish cycling at 19 kilometres an hour from cycling at 24, and a MET value drawn from indirect calorimetry, measuring the oxygen a person actually consumed while doing it. Where no measurement existed, the compilers estimated by analogy with a similar activity and said so.

This calculator uses the widely cited 2011 values, which remain the reference point for most published research and for the physical activity questionnaires used in national health surveys. The 2024 adult update revised a number of entries and added new ones; where it differs, the differences are generally smaller than the error you carry from being an individual rather than an average.

• 1 MET ≈ 3.5 ml O₂ per kg per minute ≈ 1 kcal per kg per hour.
• Under 3 METs is light activity, 3 to just under 6 is moderate, 6 and above is vigorous.
• The compendium describes intensity in measurable terms (speed, grade, effort), not in words like 'hard'.

Gross versus net, and why it matters if you eat exercise calories back

The standard MET equation gives a gross figure: the total energy your body used during the session, including the portion it would have used had you stayed on the sofa. Subtract one MET (your resting baseline) and you get the net figure, the extra the activity genuinely cost you. That is the number almost nobody publishes, and it is the one that matters most.

The gap is not trivial, and it is largest exactly where people care. A 45-minute walk at 3.5 METs is nearly 29 per cent resting metabolism; more than a quarter of the 'calories burned' on the display is simply the cost of being alive for three quarters of an hour. At 10 METs the resting share falls to 10 per cent. So the lower the intensity and the longer the session, the more a gross figure flatters you.

This matters the moment you combine it with anything else. A total daily energy expenditure figure already counts your resting metabolism for all 24 hours, and an activity multiplier on top of it already assumes some exercise. Adding a gross session figure to that total double-counts the resting portion once and the planned activity twice. If you are eating exercise calories back against a target, use the net figure, and expect even that to be generous.

Why your bodyweight is in the equation

Because a MET is defined per kilogram, body mass enters the calculation directly and linearly. A 100 kg person walking the same route at the same speed as a 60 kg person burns about 67 per cent more energy doing it, which is one reason the same daily walk produces visible change for one person and not another. It is also why calorie figures printed on a gym machine that never asked your weight cannot be right for you except by accident.

The linear assumption is a good approximation for weight-bearing activity (walking, running, stair climbing, hiking with a pack) where every kilogram must be lifted and moved. It is weaker for supported activity. On a bicycle, in a pool or on a rowing machine, part of your mass is carried by the frame or the water, so cost rises with mass more slowly than the equation implies. Swimming is the clearest case: technique changes the energy cost of a length far more than body mass does.

There is a second wrinkle in the baseline itself. Treating one MET as one kilocalorie per kilogram per hour assumes resting metabolic rate scales evenly with total mass, and it does not: fat tissue is metabolically quieter than muscle and organ tissue, so measured resting metabolic rate per kilogram falls as body mass rises. For a heavier person the true resting share is a little smaller than the equation assumes, which nudges the net figure up slightly. It is a small effect next to the 15 to 30 per cent uncertainty on the MET value, but it is one reason no MET-based estimate should be read to the nearest calorie.

How accurate a MET estimate is for one person

A published MET value is the average of a group of people doing a described activity. You are not that group. The realistic error band for an individual session is roughly 15 to 30 per cent either side, and for some activities it is wider still. The variation is not random noise: most of it comes from identifiable sources, which means you can at least tell which direction your own figure is likely to be wrong in.

Movement economy is the largest of them. A trained runner consumes noticeably less oxygen than a novice at the same pace, because years of running have made the movement more efficient; the fitter you are at a given activity, the fewer calories that activity costs you. Technique does the same job in skill-dependent sports, and in swimming it dominates everything else. Then come the conditions: gradient, surface, wind, heat, humidity, altitude, and any load you were carrying.

Finally there is the honest question of how much of the session was actually the activity. The compendium entry for weight training assumes you are training, not standing between sets with your phone. An hour in the gym is rarely an hour of work, and an hour of tennis includes a good deal of picking up balls. Enter the minutes you were genuinely moving, and the estimate improves more than any refinement of the arithmetic could manage.

• Fitness and technique: better economy means fewer calories for the same output.
• Terrain and grade: a five per cent hill changes walking cost far more than walking speed does.
• Heat, humidity and altitude: all raise the cost of the same work.
• Picking the right compendium entry matters more than the arithmetic: one step in effort is often a 25 per cent change.

Why fitness trackers and cardio machines read high

Three things stack up in the same direction. First, almost everything consumer-facing reports gross calories, for the plain reason that the bigger number is the more satisfying one. Second, wrist-worn devices estimate energy expenditure from heart rate and motion, and that inference is far harder than measuring heart rate. In a laboratory comparison of seven wrist-worn devices against indirect calorimetry, six achieved a median heart-rate error below five per cent during cycling, but none estimated energy expenditure to within 20 per cent, and the error was worse for walking, for higher body mass and for darker skin tones.

Third, gym machines infer work from what they can see. A bicycle ergometer or a rowing machine can measure mechanical power directly, which makes them the most trustworthy displays in the room. A treadmill knows speed and grade and applies a generic economy equation. An elliptical or a stair machine knows neither your stride nor your body mass unless you typed it in, and many default to something around 70 kilograms when you do not.

None of this makes a tracker useless. Trends from a device worn consistently are informative even when the absolute level is wrong, because the error is fairly stable for the same person doing the same thing. Use the device to compare this week with last week, and use a MET estimate to sanity-check whether the absolute figure is plausible.

Where exercise sits in total daily energy expenditure

Resting metabolism is the bulk of what most people spend (commonly 60 to 70 per cent of the daily total), with the thermic effect of food adding around ten per cent and all movement making up the rest. A 300 kilocalorie session on a 2,500 kilocalorie day is about twelve per cent of it. That is worth having, but it is not the lever most people imagine it to be, and it explains why a training block alone rarely moves the scale much.

There is also compensation, and it works against you twice. Behaviourally, people who train hard tend to move less for the remainder of the day (fewer stairs, more sitting, less fidgeting), and appetite often rises to meet part of the deficit. Physiologically, the picture is stranger: a large study of total energy expenditure across populations found that expenditure rises with activity only up to a point and then plateaus, so the most active people did not spend proportionally more than the moderately active ones. Whatever the mechanism, the practical consequence is the same. Exercise energy is not simply added on top.

The useful conclusion is not that exercise fails to matter (it is among the best predictors of long-term health there is) but that it should be planned as part of your total, not as a credit account. Work out your total daily energy expenditure with the activity level you genuinely live at, plan any deficit from that total, and treat this page's figure as a way of comparing sessions rather than as calories you have earned.

Using MET-minutes against the weekly guidance instead of chasing calories

MET-minutes are MET value multiplied by minutes, and they are a better unit for almost every purpose that is not eating. They need no body mass, no assumption about your resting metabolism and no calorimetry model, so almost all of the error discussed above disappears. They are also what physical activity epidemiology is actually written in, which means your own figure can be read against the research directly.

The World Health Organization's 2020 guidelines ask adults for 150 to 300 minutes of moderate-intensity aerobic activity a week, or 75 to 150 minutes of vigorous activity, or an equivalent mix, plus muscle-strengthening work on two or more days. The intensity thresholds are the same 3 and 6 MET lines used throughout this page, which is what makes the translation possible: a 45-minute session at 6 METs is 270 MET-minutes, and two of those in a week clears the minimum.

Converting the guideline into MET-minutes is approximate, and it is worth knowing why. The answer depends on which MET value you assume 'moderate' means. At the bottom of the moderate band, around 3.3 METs, 150 to 300 minutes works out at roughly 500 to 1,000 MET-minutes, the range this calculator uses. The guideline's own dose-response analysis uses 750 MET-minutes a week as the equivalent of the 150-minute minimum, because it assumes a higher average intensity. Either way, the practical target is a band rather than a line, and the reassuring finding running through all of it is that the steepest health gains come at the bottom end: the move from doing nothing to doing something is worth far more than the move from a lot to slightly more.

• MET-minutes = MET × minutes. No weight, no calorimetry assumption, no compounding error.
• WHO adult target: 150–300 minutes moderate, or 75–150 minutes vigorous, or an equivalent combination, per week.
• Muscle-strengthening activity on two or more days a week sits alongside the aerobic target, not inside it.
• Some activity is better than none, and the largest returns come at the low end of the range.

How it's calculated

Worked example: an 80 kg adult running 9.7 km/h for 30 minutes

1. Look up the activity: running at 9.7 km/h (6 mph, a 10-minute mile) is 9.8 METs in the compendium.
2. Gross kilocalories per minute: 9.8 × 3.5 × 80 ÷ 200 = 2,744 ÷ 200 = 13.72 kcal/min.
3. Gross for the session: 13.72 × 30 = 411.6 kcal, the figure a watch or treadmill would show.
4. Net kilocalories per minute: (9.8 − 1) × 3.5 × 80 ÷ 200 = 8.8 × 3.5 × 80 ÷ 200 = 12.32 kcal/min.
5. Net for the session: 12.32 × 30 = 369.6 kcal. The 42 kcal difference is resting metabolism, what those 30 minutes would have cost sitting down.
6. Apply the error band: at ±15–30% the honest statement is 'somewhere between roughly 260 and 480 kilocalories of extra energy', most likely near 370.
7. MET-minutes: 9.8 × 30 = 294. At 9.8 METs this is vigorous activity, so three to five sessions of this length would meet the 75–150 minute weekly guideline.
8. Fat-energy equivalent: 369.6 ÷ 7,700 = 0.048 kg, or 48 grams. That is what the energy converts to on paper, not what one run removes from your body.
9. The calculator displays calorie figures rounded to the nearest ten (370 and 410 here) because the underlying MET value is nowhere near precise enough to justify a decimal place.

Where this number is used in the real world

• Building a training week against the weekly activity guideline, counting MET-minutes rather than calories.
• Comparing how to spend the same hour: the relative ordering between activities is far more reliable than any single figure.
• Sanity-checking what a watch or a cardio machine claims, particularly when the machine never asked your body mass.
• Cardiac rehabilitation and exercise prescription, where METs are the standard currency for grading and clearing activity.
• Occupational and functional capacity assessment, where exercise-test results are reported in METs and matched to the demands of a job.
• Public health surveillance and research, where self-reported activity questionnaires are scored in MET-minutes per week.
• Deciding how much of a session, if any, to eat back while running a planned calorie deficit.

Frequently asked questions

Keep going

A single number rarely tells the whole story. Alongside the calories burned result, the TDEE calculator, the calorie deficit calculator, the BMR calculator and the macros calculator each add a different angle on the same measurements. For the reasoning behind the numbers, read TDEE explained and BMI vs body fat vs waist.

Sources

1. Ainsworth BE, Haskell WL, Herrmann SD, et al. 2011 Compendium of Physical Activities: a second update of codes and MET values. Med Sci Sports Exerc 2011;43(8):1575–81. doi.org/10.1249/MSS.0b013e31821ece12
2. Herrmann SD, Willis EA, Ainsworth BE, et al. 2024 Adult Compendium of Physical Activities: a third update of the energy costs of human activities. J Sport Health Sci 2024;13(1):6–12. doi.org/10.1016/j.jshs.2023.10.010
3. Compendium of Physical Activities: the maintained MET value tables (Adult, Older Adult and Wheelchair compendia). pacompendium.com/
4. WHO guidelines on physical activity and sedentary behaviour. World Health Organization, Geneva, 2020. www.who.int/publications/i/item/9789240015128
5. Jetté M, Sidney K, Blümchen G. Metabolic equivalents (METS) in exercise testing, exercise prescription, and evaluation of functional capacity. Clin Cardiol 1990;13(8):555–65. doi.org/10.1002/clc.4960130809
6. Shcherbina A, Mattsson CM, Waggott D, et al. Accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure in a diverse cohort. J Pers Med 2017;7(2):3. doi.org/10.3390/jpm7020003
7. Pontzer H, Durazo-Arvizu R, Dugas LR, et al. Constrained total energy expenditure and metabolic adaptation to physical activity in adult humans. Curr Biol 2016;26(3):410–17. doi.org/10.1016/j.cub.2015.12.046
8. LaForgia J, Withers RT, Gore CJ. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. J Sports Sci 2006;24(12):1247–64. doi.org/10.1080/02640410600552064