Knowing roughly how many calories an activity burns helps you plan training, fuel workouts, and understand the energy side of weight management. A calories burned calculator turns your activity, body weight, and time into a quick estimate so you don't have to guess.
FORMA's calculator is free, works in metric and US units, and updates live as you type. It uses MET values (Metabolic Equivalent of Task), the same standard researchers and fitness apps rely on, so your numbers stay grounded in published activity data rather than rough rules of thumb.
How the calories burned calculator works
This calculator uses the MET (Metabolic Equivalent of Task) method, the standard way exercise energy is estimated. The exact formula is:
calories = MET × weight (kg) × (minutes ÷ 60)
A MET is a measure of how intense an activity is relative to sitting still (1 MET). The harder the activity, the higher its MET value. You pick an activity from the list, and each one carries a fixed MET rating, for example running at 8 km/h is 8.3 MET and vigorous weightlifting is 6 MET. The calculator then multiplies that MET value by your body weight in kilograms and by the fraction of an hour you exercised (minutes divided by 60).
You need three inputs: the activity (which sets the MET), your body weight, and the duration in minutes. If you enter weight in pounds, it's converted to kilograms internally. Because heavier bodies burn more energy at the same intensity, weight scales the result directly.
Worked example
Suppose you weigh 70 kg and run at 8 km/h (MET = 8.3) for 30 minutes.
Plug into the formula: calories = 8.3 × 70 × (30 ÷ 60) calories = 8.3 × 70 × 0.5 calories = 581 × 0.5 calories = 290.5, about 291 calories burned.
Run the full hour instead and you'd double it to roughly 581 calories. Swap in vigorous weightlifting (MET = 6) at 80 kg for 45 minutes and you get 6 × 80 × 0.75 = 360 calories.
Things to keep in mind
- MET values are population averages, so two people of the same weight doing the same activity can burn noticeably different amounts based on fitness, efficiency, and technique.
- The formula uses total body weight, not body composition, so it doesn't account for how muscle versus fat affects your individual metabolism.
- It estimates gross calories burned during the activity and doesn't subtract the calories you'd have burned at rest, nor does it add the smaller after-exercise (EPOC) burn.
- Real-world intensity varies, hills, pace changes, and rest breaks all shift the true number, so treat the result as a solid estimate rather than an exact measurement.
Frequently asked questions
How accurate is a calories burned calculator?
MET-based estimates are reliable for planning but not exact. They use average values for each activity, so your real burn can vary by 10 to 20 percent depending on fitness, intensity, terrain, and individual metabolism. Use the number as a consistent guide rather than a precise measurement.
What is a MET value?
MET stands for Metabolic Equivalent of Task. One MET is the energy you use sitting at rest. An activity rated at 8 MET burns about eight times that. Higher MET values mean higher intensity, which is why running scores higher than walking in the formula.
Does body weight affect calories burned?
Yes. The formula multiplies directly by your weight in kilograms, so a heavier person burns more calories doing the same activity for the same time. That's why weight is a required input alongside the activity's MET value and your duration.
Why does the calculator ask for minutes?
Duration scales the result through the (minutes ÷ 60) term, which converts your time into a fraction of an hour. Exercising twice as long burns roughly twice the calories at the same intensity, so accurate timing gives you a better estimate.
Do these calories include my resting metabolism?
The MET formula estimates gross calories burned during the activity, which includes the small amount you'd burn at rest in that time. For your full daily energy needs, pair this with a BMR or TDEE calculator to see your baseline plus activity.