Calories burned by activity: how the estimate is made

The MET model: energy in multiples of rest

MET stands for metabolic equivalent of task. By convention, 1 MET is resting energy expenditure while seated, roughly 3.5 mL of oxygen per kilogram of body weight per minute, or about 1 kcal per kg per hour. An 8-MET activity costs eight times that resting rate. So MET becomes an “intensity label” independent of your weight: brisk walking is ~5 MET for anyone; weight enters later, when converting to calories. The model’s great strength is putting unlike things on one scale, cycling, swimming and stair-climbing all get a number you can line up side by side.

MET

The ratio of an activity’s expenditure to resting expenditure. 1 MET = rest; 10 MET = ten times as intense. It is a dimensionless number, a ratio, not a measurement of you.

Resting VO₂

Oxygen consumption at rest, conventionally set at 3.5 mL/kg/min, the basis of the calculation. It was calibrated on a reference 70 kg, 40-year-old man.

Caloric equivalent of O₂

About 5 kcal are released per liter of oxygen consumed (it ranges ~4.8 to ~5.0 depending on the fuel burned); this is what closes the conversion into calories.

MET did not fall from the sky: it was tabulated. The Compendium of Physical Activities assigned a value to hundreds of activities from calorimetry measurements, and became the reference almost every app and spreadsheet quietly uses. It has been updated three times since it launched, and some numbers changed along the way.

1. 1993First compendium

   Ainsworth and colleagues publish the original version, coding the energy cost of activities in MET to standardize epidemiology studies.

2. 2000First update

   The list is expanded and codes revised, consolidating the compendium as an international reference.

3. 2011Second update

   The 2011 version is the one most calculators (including the one on this page) still use. Running at 10 km/h becomes 9.8 MET; brisk walking, 5.0 MET.

4. 2024Third update

   The “2024 Adult Compendium” lists 1,114 activities, 303 of them new, and revises 176 MET values, including removing estimates specific to older adults. Not every calculator has migrated.

The formula (and where each number comes from)

The calories-burned-by-activity calculator uses the MET-based metabolic equation. The lower line is net expenditure, which subtracts rest, we come back to it later.

The “200” is not magic, you can derive it in four steps. First, oxygen consumption per minute is MET × 3.5 × weight, in milliliters (because 3.5 is already mL/kg/min and you multiply by kilograms). Second, divide by 1000 to go from milliliters to liters per minute. Third, multiply by ~5 kcal, the energy released per liter of O₂. Fold the last two together: multiplying by 5 and dividing by 1000 is the same as dividing by 200, because 1000 ÷ 5 = 200. What remains is kcal/min = (MET × 3.5 × weight) ÷ 200. The whole formula is just oxygen turning into heat.

Worked example 1, the same run, two weights. Running at 10 km/h is worth 9.8 MET; assume 30 minutes. For 60 kg: kcal/min = (9.8 × 3.5 × 60) ÷ 200 = 2,058 ÷ 200 = 10.29 kcal/min; over 30 min, ≈ 309 kcal. For 90 kg: kcal/min = (9.8 × 3.5 × 90) ÷ 200 = 3,087 ÷ 200 = 15.44 kcal/min; over 30 min, ≈ 463 kcal. Notice the exact linearity: 90 ÷ 60 = 1.5, and indeed 463 ÷ 309 = 1.5. Expenditure is directly proportional to weight, no curves, no magic; moving a body 50% heavier costs 50% more oxygen at the same pace.

Worked example 2, gross vs. net, the calories that “disappear”. Brisk walking (5.0 MET), 70 kg, 45 minutes. Gross: kcal/min = (5.0 × 3.5 × 70) ÷ 200 = 1,225 ÷ 200 = 6.13 kcal/min; over 45 min, ≈ 276 kcal, this is what the calculator shows. Net: use (5.0 − 1) instead of 5.0: (4.0 × 3.5 × 70) ÷ 200 = 980 ÷ 200 = 4.9 kcal/min; over 45 min, ≈ 221 kcal. Difference: 276 − 221 = 55 kcal. Those 55 kcal are exactly the 1 MET of rest you would spend seated over the same 45 minutes (1 × 3.5 × 70 ÷ 200 × 45 = 55). In other words, ~20% of the number “disappears” once you count only what the exercise added.

MET of common activities

These are the MET values the calculator applies, all from the Compendium of Physical Activities (2011 edition, still the most used in software). Use them to compare intensities: doubling the MET doubles the per-minute expenditure.

Translating MET into calories for a fixed weight makes the difference in magnitude obvious. The chart below uses a 70 kg person (the model’s reference weight) and the formula kcal/hour = MET × 3.5 × 70 ÷ 200 × 60 = MET × 73.5. Jumping rope at 11 MET spends more than four times an hour of yoga, but almost nobody jumps rope for an hour, which is why duration and sustainable intensity matter as much as the MET.

Try it in the tool itself: change the weight and duration and watch the total move. It also shows quick references (per 30 min, per hour) and illustrative equivalences.

Why 3.5 doesn’t fit everyone

Here is the bias almost no calculator mentions. The 3.5 mL/kg/min of 1 MET was taken from a 70 kg, 40-year-old man and then generalized to all of humanity. But resting expenditure per kilogram falls with age, is lower on average in women, and is diluted by more body fat (fat consumes very little oxygen at rest). Byrne and colleagues (2005) measured the real resting rate of 769 adults and found an average of 2.6 mL/kg/min, about 26% below the standard. Put the other way around, the conventional value of 3.5 overestimates true rest by ~35%.

Because that 3.5 multiplies everything, the error propagates: if your true rest is 2.6 rather than 3.5, each MET represents a larger fraction of your metabolism than the model assumes, and the reported expenditure tends to come out inflated, more so for women, older people and people with more body fat. It is not the only reason the number is approximate; the list below gathers the heaviest ones.

• Fitness and technique: an efficient runner spends less energy at the same pace than a beginner.
• Body composition: more lean mass raises expenditure and more fat dilutes it, and MET is blind to this, see BMI vs. body-fat percentage.
• Age and sex change the real cost of the same activity, exactly what the fixed 3.5 ignores.
• Terrain, incline, wind, heat and altitude alter the effort of the same “type” of exercise.
• The caloric equivalent of O₂ (5 kcal/L) is an average too; it varies with the fuel burned (~4.8 to ~5.0).

Activity expenditure vs. TDEE (and the “eating it back” mistake)

The classic “eating the workout back” mistake comes from three improper additions at once: the number is gross (not net), the TDEE you already use usually presumes training, and the body compensates part of the burn. If your TDEE uses an “active” factor, that factor already assumes you train, so adding every session’s calories on top double-counts part of the expenditure. Either use a lower TDEE (sedentary/light) and add workouts by their net value, or use a higher TDEE and do not add them. To calibrate intensity and stay in the right zone, the target heart rate helps, see also heart-rate zones. And for the BMR-and-TDEE logic behind all this, the guide BMI, BMR and TDEE.

And the “10,000 steps”?

The 10,000-steps goal on your watch did not come from any study. It came from marketing: in 1965 the Japanese company Yamasa launched a pedometer called Manpo-kei, literally “10,000-step meter”, riding the enthusiasm after the 1964 Tokyo Olympics. The number was a round, memorable slogan, not a scientific finding. The science came later, and it pointed to lower values.

Lee and colleagues (2019, JAMA Internal Medicine) followed 16,741 women with a mean age of 72. Compared with the lowest-step quartile (median 2,718/day), women at about 4,363 steps/day already had ~41% lower risk of death (hazard ratio 0.59), and the benefit kept improving until it leveled off around 7,500 steps/day, well below 10,000. The meta-analysis by Paluch and colleagues (2022, Lancet Public Health), with 47,471 adults and 3,013 deaths, found the same shape: risk falls with more steps until a plateau around 6,000–8,000/day for people aged 60+ and 8,000–10,000/day for younger adults. The message is consistent: more steps help, the biggest gain is leaving sedentarism behind, and there is nothing magical about 10,000.

The link to this guide is direct: counting steps and counting calories suffer from the same misunderstanding. They are useful rulers to compare and to keep moving, but round target numbers hide averages and biases. Use them to build a habit, not to chase a decimal place.