How Many Calories Does Exercise Burn? The MET Method Explained

A MET (metabolic equivalent of task) expresses the intensity of an activity as a multiple of the energy you use sitting still. One MET is defined as an oxygen uptake of 3.5 millilitres per kilogram of body weight per minute, roughly 1 kcal per kilogram per hour. An activity rated at 7 METs costs about seven times as much energy per minute as resting.

kcal per minute = MET × body weight in kg × 3.5 ÷ 200

The 3.5 is the oxygen cost of one MET in millilitres. Dividing by 1,000 converts it to litres, and the body releases about 5 kcal per litre of oxygen used; together those two steps become the division by 200. Multiply by the minutes exercised for the session total.

Example: a 75 kg runner at 9.7 km/h (6 mph) works at about 9.8 METs. 9.8 × 75 × 3.5 ÷ 200 = 12.9 kcal per minute, or about 386 kcal in 30 minutes.

MET values come from the Compendium of Physical Activities, first published by Barbara Ainsworth and colleagues in 1993 and revised several times since. A common shortcut, used by the calorie burn timer, treats one MET as exactly 1 kcal per kilogram per hour. It gives figures about 5 per cent lower, well inside the margin of error of either.

The table applies the formula to 30 minutes of continuous activity, using values from the 2011 Compendium, rounded to the nearest kilocalorie.

Activity	METs	60 kg	75 kg	90 kg
Hatha yoga	2.5	79	98	118
Walking, 4.8 km/h (3 mph)	3.5	110	138	165
Weight training, moderate	3.5	110	138	165
Brisk walking, 6.4 km/h (4 mph)	5.0	158	197	236
Swimming laps, easy to moderate	5.8	183	228	274
Cycling, 16–19 km/h	6.8	214	268	321
Rowing machine, 100 W	7.0	221	276	331
Circuit training, vigorous	8.0	252	315	378
Running, 8 km/h (5 mph)	8.3	261	327	392
Running, 9.7 km/h (6 mph)	9.8	309	386	463
Jumping rope, moderate	11.8	372	465	558

The formula is linear, so 45 minutes is the 30-minute figure × 1.5, and 120 kg is double the 60 kg column. Three things stand out:

• Weight matters as much as the activity. A 90 kg person walking briskly (236 kcal) burns more than a 60 kg person swimming laps (183 kcal).
• Intensity sets the rate; duration sets the total. An hour of brisk walking at 75 kg (394 kcal) beats 30 minutes of running at 8 km/h (327 kcal).
• These are gross figures. They include the 1 MET you would burn on the sofa anyway, about 39 kcal per 30 minutes at 75 kg. The extra cost of the exercise is (MET − 1) × kg × 3.5 ÷ 200: 98 kcal for the walk, not 138.

To pick the right running row, work out your pace with the pace calculator: 7:30 per km is 8 km/h, and about 6:12 per km is 9.7 km/h.

Fitness trackers do not measure calories. They measure wrist movement and heart rate and feed both into equations built from group averages. A widely reported 2017 Stanford study of seven wrist-worn devices found most measured heart rate to within about 5 per cent, but none estimated energy expenditure to within 20 per cent; the best was off by an average of 27 per cent, the worst by 93. The reasons are structural:

• Heart rate is not only work. Heat, dehydration, caffeine and stress raise it without raising energy use, while fitter people have lower heart rates at the same workload.
• Wrist motion misses load. Cycling, rowing and uphill walking involve a lot of work with modest arm movement.
• Optical sensors struggle with loose straps, cold skin, tattoos and the rapid intensity changes of interval training.
• Labels differ. Some apps show "active" (net) calories, others total (gross), so brands are not comparable.

Gym machines use a default weight unless you enter yours, and cannot tell that you are holding the handrails, which takes a large share of the effort off your legs. The MET method has its own bias: direct measurements find the textbook 3.5 ml/kg/min too high for many adults, especially heavier and older people, so table figures tend to run high for them.

After exercise, breathing and heart rate take a while to settle. You keep using extra oxygen to refill the muscles' fuel stores, clear lactate, shed heat and start repairs. This is excess post-exercise oxygen consumption (EPOC), the "afterburn" of gym marketing.

It is real, but small. Its size depends mainly on intensity, and research reviews put it at roughly 6 to 15 per cent of the net energy cost of the session. A hard 300 kcal interval workout might add 20 to 45 kcal over the following hours; an easy walk adds a handful. Claims of burning for 24 or 48 hours describe a slight elevation, not a meaningful total.

Tabata and HIIT intervals are still worth doing because they are time-efficient and build fitness quickly. Count the session, not the afterburn. The interval timer and Tabata timer handle the work and rest phases.

1. Read every number as a range. Treat 300 kcal as somewhere between 240 and 360: useful for comparing sessions, not for exact accounting.
2. Stick with one method. A trend from one device or formula is more trustworthy than its absolute values.
3. Do not eat back every calorie. Gross figures and optimistic trackers both overstate what exercise adds. A common rule of thumb is to add back no more than half.
4. Measure the input you control. Log real minutes of work with the workout timer or stopwatch, not the total time spent in the gym.
5. Let the scale settle arguments, slowly. Weight swings by a kilogram or more day to day with water and food; the two-to-four-week average shows your real energy balance.

The calorie burn timer takes your activity and weight and adds up the total as the clock runs. Use it as a consistent yardstick rather than a precise measurement.