Activity Energy Estimator
Estimate energy used in an activity from MET values, weight, and duration.
What a MET value actually represents
One MET is the energy cost of sitting quietly — approximately 3.5 millilitres of oxygen per kilogram of body weight per minute. An activity rated at 8 METs costs roughly eight times that. Multiplying METs by body weight and duration gives a workable estimate of total energy expenditure, which is why the compendium of MET values underpins nearly every calorie estimate you will see in an app or on a machine.
The catch is that published MET values are population averages measured on modest samples. Individual efficiency varies substantially with fitness, technique, and biomechanics — a trained cyclist covers the same distance for meaningfully less energy than a novice.
Every estimate here has wide error bars
Errors of 20 to 30% against laboratory measurement are normal for MET-based estimates, and wearable devices do no better on average despite reporting to the calorie. Cardio machines are typically worse still, often overestimating substantially, and many do not account for body weight at all. Treat any single figure as an order of magnitude rather than a measurement.
There is also a subtler issue: gross energy expenditure includes the energy you would have burned anyway just being alive during that hour. The net additional cost of exercise is lower than the gross figure by roughly one MET-hour per hour, which matters when the number is being used against a food intake target.
Exercise is a weak lever for weight, a strong one for health
Energy expenditure from exercise is smaller than most people assume relative to daily intake, and there is decent evidence of partial compensation — activity elsewhere in the day drops and appetite rises, offsetting part of the deficit. Using these numbers to justify eating back the calculated burn tends not to work. The health benefits of activity — cardiovascular fitness, insulin sensitivity, mood, bone density, mortality risk — are large and largely independent of whether weight changes at all.
How to use it
- Enter your body weight, the activity, and the duration in minutes.
- Read the result as a broad range, not a precise figure — assume ±25%.
- Subtract roughly one MET-hour per hour if you need the net rather than gross cost.
- Use it to compare activities against each other rather than to balance a food diary.
Common questions
How accurate is this estimate?
Errors of 20–30% against laboratory measurement are typical for MET-based calculations, because published MET values are population averages and individual efficiency varies. Treat the output as a range, not a measurement.
Why does my watch or treadmill report a different number?
Different devices use different models, and many cardio machines overestimate substantially — some ignore body weight entirely. No consumer device measures energy expenditure directly; all of them estimate.
What is the difference between gross and net calories?
Gross includes the energy you would have burned at rest during the same period. Net is the additional cost of the activity, roughly one MET-hour per hour lower, and is the more meaningful figure when comparing against food intake.
Can I eat back the calories I burned?
It rarely works as expected. Estimates run high, appetite tends to rise after exercise, and unconscious activity often falls, so the real deficit is smaller than the numbers suggest. The health benefits of exercise do not depend on this arithmetic.
Disclaimer: These estimates are general information, not medical advice, diagnosis, or treatment. Population formulas do not account for individual physiology, medication, or medical conditions. Consult a qualified clinician about your own health, and seek immediate care for any urgent symptom.