Exercise scientists rate activities in METs — metabolic equivalents. One MET is the energy you burn sitting quietly, about 1 kcal per kilogram of body weight per hour. Running at 6 mph is 9.8 METs, so it burns roughly ten times your resting rate. The values here come from the 2011 Compendium of Physical Activities, the reference used by fitness trackers, research studies and most calorie calculators.
The formula is calories = MET × 3.5 × weight (kg) ÷ 200 × minutes. The 3.5 is resting oxygen consumption in ml/kg/min, and dividing by 200 converts oxygen to kilocalories. A 70 kg (155 lb) person running at 6 mph for 30 minutes burns 9.8 × 3.5 × 70 ÷ 200 × 30 ≈ 360 calories. Heavier bodies burn more for the same activity because moving more mass takes more energy, which is why weight is the second input.
Gross versus net. The headline figure is gross calories — everything you burned during the session, including what you would have burned anyway just being alive. The "above resting" figure subtracts that baseline (1 MET) and is the fairer number for "how much extra did this workout cost?". For weight-management maths, net is the more honest figure; most apps and machines quote gross.
How accurate is it? MET values are population averages. Fitness level, technique, terrain, temperature and body composition all shift real expenditure by ±10–20%. A brisk walk feels different for a beginner and a marathoner, but the MET table gives both the same number. Treat results as a good estimate for planning, not a lab measurement; a chest-strap heart-rate monitor or metabolic cart is needed for individual precision.
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Frequently asked questions
How many calories does running burn?
Roughly 100 calories per mile for a 155 lb person, a bit more the heavier you are. At 6 mph (10-minute miles) that is about 360 calories in 30 minutes; at 8 mph about 430. The calculator uses the exact MET value for each pace.
How many calories does walking burn?
A brisk 3.5 mph walk burns about 150 calories in 30 minutes for a 155 lb person (MET 4.3). Slower 2.5 mph walking is about 105 calories for the same time.
What is a MET?
Metabolic equivalent of task. 1 MET = resting energy use, about 1 kcal per kg of body weight per hour. An activity rated 6 METs burns six times your resting rate. Values come from the Compendium of Physical Activities.
Why does my fitness tracker show a different number?
Trackers combine heart rate, accelerometer data and their own algorithms, and many report net rather than gross calories. Differences of 10–25% between any two methods are normal. Neither is exact; consistency matters more than the absolute figure.
Does muscle burn more calories than fat during exercise?
At rest, slightly. During exercise the main driver is total body mass and intensity, which is why the formula uses weight rather than body-fat percentage. Two people of equal weight doing the same workout get the same estimate here.
Can I enter my own MET value?
Yes — choose 'Custom MET value' at the bottom of the activity list and type any MET, for example from the full Compendium (which lists more than 800 activities).