How accurate is a calories burned calculator?

It is a solid estimate, not a measurement. MET values describe an average person at a steady effort, so your real burn can differ by 10 to 20 percent with fitness level, technique, and how much you pause. Use it to compare sessions and stay consistent, not to eat back every calorie it shows.

MET stands for metabolic equivalent of task. One MET is the energy you use at rest, about 3.5 milliliters of oxygen per kilogram of bodyweight per minute. Running at 10 km/h is rated 9.8 MET, so it costs almost ten times your resting energy for as long as you hold it.

How many calories does weightlifting burn?

Fewer than most people hope. A typical gym session sits near 3.5 MET, which is around 220 kcal per hour for an 80 kg lifter, because most of the session is rest between sets. Vigorous lifting or circuit training with short rests can roughly double that. The real value of lifting is the muscle it builds, not the calories it burns.

Why does my gym machine or watch show a higher number?

Machines assume a generic body and often include your resting burn in the total. Wrist trackers guess from heart rate, which strength training, heat, and stress push up without a matching energy cost. Overreports of 15 to 20 percent or more are common, which is why two devices rarely agree.

Do I keep burning calories after the workout?

Yes, but less than the hype suggests. The afterburn effect is real and modest, usually around 6 to 15 percent of the session's cost, and it is largest after hard interval work or heavy lifting. It is a nice bonus, not a second workout.

Should I eat back the calories I burn?

Usually not all of them. Exercise estimates run high and most people underestimate what they eat, so eating back everything erases most of the deficit. If you are cutting, treat exercise calories as a buffer rather than a budget, and judge progress by the scale and the mirror over weeks.

Free calories burned calculator

Know what your session
really burned.

Pick from 80 activities, enter your weight and time, and get an estimate built on published MET values instead of a flattering machine display. Free, instant, no signup.

Units

WeightkgDurationmin

Activity

Calories burned

617

kcal

Running, 10 km/h, MET value 9.8.

Around 412 kcal per 30 minutes at your weight.

The same session, other activities

Swimming freestyle, fast: 617 kcal
Cycling, 22 to 26 km/h: 630 kcal
Football, competitive: 630 kcal

These are estimates for an average body at a steady effort. Pauses, technique, and fitness level all move the real number. MET values come from the Compendium of Physical Activities.

Calories burned

617 kcal That number is the input.

Where the muscle goes is the output. See it with a free physique scan.

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How to calculate calories burned

Pick an activity, enter your bodyweight and how long you trained, and read an estimate of the energy you spent, built on published MET values.

1
Pick your activity
Search the list and select what you did. Every activity carries a MET value from the Compendium of Physical Activities.
2
Enter your weight and duration
Add your bodyweight in metric or imperial units and how many minutes the session lasted.
3
Read your estimate
See the total calories burned, a per-30-minutes reference, and how nearby activities compare over the same session.

Behind the number

One honest formula beats a flattering display.

What a MET value means

One MET is the energy your body uses sitting at rest. An activity rated 8 costs roughly eight times that. The calculator multiplies the MET value by your weight and your minutes, so every estimate stays anchored to measured data instead of marketing.

Why machines overreport

Cardio machine displays often run 15 to 20 percent high, sometimes more. They assume a generic body, keep counting while you coast, and ignore that you lean on the handles. A MET-based estimate is not perfect, but it does not flatter you.

Why weight dominates

Calories are the cost of moving your body, so the formula scales directly with bodyweight. A 90 kg lifter burns half as much again as a 60 kg lifter in the same session. It is also why the same run gets cheaper as you get leaner.

Questions, answered

Calories burned, explained.

How accurate is a calories burned calculator?: It is a solid estimate, not a measurement. MET values describe an average person at a steady effort, so your real burn can differ by 10 to 20 percent with fitness level, technique, and how much you pause. Use it to compare sessions and stay consistent, not to eat back every calorie it shows.
What is a MET?: MET stands for metabolic equivalent of task. One MET is the energy you use at rest, about 3.5 milliliters of oxygen per kilogram of bodyweight per minute. Running at 10 km/h is rated 9.8 MET, so it costs almost ten times your resting energy for as long as you hold it.
How many calories does weightlifting burn?: Fewer than most people hope. A typical gym session sits near 3.5 MET, which is around 220 kcal per hour for an 80 kg lifter, because most of the session is rest between sets. Vigorous lifting or circuit training with short rests can roughly double that. The real value of lifting is the muscle it builds, not the calories it burns.
Why does my gym machine or watch show a higher number?: Machines assume a generic body and often include your resting burn in the total. Wrist trackers guess from heart rate, which strength training, heat, and stress push up without a matching energy cost. Overreports of 15 to 20 percent or more are common, which is why two devices rarely agree.
Do I keep burning calories after the workout?: Yes, but less than the hype suggests. The afterburn effect is real and modest, usually around 6 to 15 percent of the session's cost, and it is largest after hard interval work or heavy lifting. It is a nice bonus, not a second workout.
Should I eat back the calories I burn?: Usually not all of them. Exercise estimates run high and most people underestimate what they eat, so eating back everything erases most of the deficit. If you are cutting, treat exercise calories as a buffer rather than a budget, and judge progress by the scale and the mirror over weeks.

Calories are half the story.

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