How the calories-burned-lifting calculation works
Weight lifting burns calories in proportion to how hard your body works and how long you work. This calculator uses the MET (Metabolic Equivalent of Task) method, the same approach used by the Compendium of Physical Activities and most fitness trackers. One MET is your resting metabolic rate, defined as an oxygen uptake of 3.5 milliliters per kilogram of body weight per minute. An activity rated at 5 METs makes you burn energy five times faster than sitting still.
The formula
The core equation is:
Calories = METs × 3.5 × body weight (kg) ÷ 200 × duration (minutes)
The constants come from exercise physiology. Oxygen consumption in ml/min equals METs × 3.5 × weight in kg. Burning one liter (1,000 ml) of oxygen releases roughly 5 kcal, so dividing ml/min by 1,000 and multiplying by 5 is the same as dividing by 200. Multiply the resulting kcal/min by your session length to get total calories. If you enter your weight in pounds, the calculator first converts it to kilograms by dividing by 2.20462.
How many METs is weight lifting?
The 2011 Compendium of Physical Activities lists resistance training at several intensities. Light-to-moderate effort (machine circuits, lighter free weights, general toning) is about 3.5 METs. A typical mixed strength session lands near 5.0 METs. Vigorous effort — heavy powerlifting or bodybuilding with challenging loads and short rest — is about 6.0 METs. The longer your rest periods between sets, the lower your effective MET value, because your heart rate falls while you recover.
Worked example
A 170 lb lifter (77.1 kg) doing a general 45-minute session at 5.0 METs burns 5.0 × 3.5 × 77.1 ÷ 200 × 45 ≈ 304 calories, or about 6.7 calories per minute. Bump the effort to 6.0 METs and the same session burns roughly 364 calories. Because the result scales directly with body weight, a 220 lb (99.8 kg) lifter doing the identical 5.0-MET session burns about 393 calories.
Why estimate calories from lifting?
Strength training raises your daily energy expenditure both during the workout and, to a smaller degree, afterward through excess post-exercise oxygen consumption (EPOC). Knowing the per-session figure helps you plan a calorie deficit for fat loss, a surplus for muscle gain, or simply reconcile your training against a daily target. Unlike steady-state cardio, lifting is intermittent, so treat the number as a session average rather than a moment-by-moment reading.