Calories burned during exercise: real figures, and what your watch gets wrong
The calories burned during exercise depend mainly on three things: your body weight, the intensity of the activity and how long it lasts. The CDC gives reference figures for a person weighing 70 kilograms: about 280 kilocalories in an hour of walking at 3.5 miles per hour, 290 for easy cycling, 510 for slow freestyle swimming and 590 for running at 5 miles per hour or cycling faster than 10 miles per hour. A light weight-lifting workout comes to about 220 kilocalories an hour, a vigorous one to about 440. Heavier people burn more for the same activity, lighter people less. To adjust for your own weight, the Compendium of Physical Activities gives each activity a MET value, where one MET is about one kilocalorie per kilogram per hour. Treat any figure, including your watch's, as an estimate: in a Stanford study, no wrist device estimated energy expenditure with an error below 20%. The figures are useful for planning, much less for counting every bite.
Put your training in the context of your whole day
Estimate what you use at rest and over a full day. Compare a session's calories with the second figure to see how much of the total it represents.
- Resting energy expenditure (Mifflin-St Jeor)
- 1,780 kcal per day
- Estimated daily needs
- 2,759 kcal per day
Mifflin-St Jeor estimate, accurate to about 10% for most people. The activity factor already includes your usual training.
Reference figures for common activities
The CDC publishes approximate values for a person of 70 kilograms. They are rounded and meant as a guide, which is exactly how to use them.
Moderate activities, per hour:
- Walking at 3.5 miles per hour (5.6 km/h): about 280 kcal.
- Cycling under 10 miles per hour (16 km/h): about 290 kcal.
- Dancing or light gardening: about 330 kcal.
- Hiking: about 370 kcal.
- Light weight-lifting workout: about 220 kcal.
Vigorous activities, per hour:
- Walking at 4.5 miles per hour (7.2 km/h): about 460 kcal.
- Aerobics or slow freestyle swimming: about 510 kcal.
- Running at 5 miles per hour (8 km/h): about 590 kcal.
- Cycling over 10 miles per hour: about 590 kcal.
- Vigorous weight lifting: about 440 kcal.
Most sessions do not last an hour of uninterrupted effort. A 30-minute circuit with rests, transitions and a warm-up uses less than half of the hourly figure for its hardest exercise.
Calculating it for your own weight
The CDC notes that calories burned are higher for people heavier than 70 kilograms and lower for lighter people. The Compendium of Physical Activities, updated in 2024 with 1,114 activities, makes the adjustment possible. It defines one MET as about one kilocalorie per kilogram of body weight per hour, roughly the cost of sitting quietly.
The calculation is therefore:
- Find the MET value of the activity in the Compendium.
- Multiply it by your weight in kilograms.
- Multiply by the duration in hours.
You can check it against the CDC: 280 kilocalories an hour of walking for 70 kilograms corresponds to 4 METs. For someone of 85 kilograms, the same walk comes to about 340 kilocalories an hour, and the run at 5 miles per hour to about 715.
One subtlety matters for weight loss. A MET figure is a gross value: it includes the one MET you would have used anyway, sitting on the sofa. The extra energy an hour of walking costs an 85 kilogram person is therefore about three METs, roughly 255 kilocalories, not 340.
Why your watch disagrees with the table
Researchers at Stanford tested seven wrist-worn devices against laboratory measurement in 60 volunteers sitting, walking, running and cycling. Most measured heart rate well. None estimated energy expenditure with an error below 20%, and the error was larger for walking, for people with a higher body mass index and for darker skin tones. The authors advised caution in using these figures in health programmes.
In practice, use your watch to compare one week with another, not to decide how much to eat tonight.
How a session fits into your whole day
Exercise is only one part of what you use in 24 hours. The calculator on this page estimates the rest: your resting expenditure with the Mifflin-St Jeor equation, then your whole day with an activity factor. For an illustrative man of 40, 85 kilograms and 180 centimetres, training three to five times a week, the equation gives about 1,780 kilocalories at rest and about 2,760 for the day.
Seen against that total, a 300 kilocalorie session matters, but it is not the main lever. There is also evidence that the body does not simply add up activity. Pontzer and colleagues found, in 332 adults, that total daily energy expenditure rose with activity at lower levels and levelled off at higher ones. More on this in metabolism and exercise.
Should you eat back what you burn?
The honest answer is: partly, and without counting precisely. Your daily activity factor already includes your usual training, so the deficit you set in calorie deficit accounts for it. Adding the watch's figure on top counts the same session twice, with a 20% margin of error.
A better rule is to eat a little more on long or hard days, keep your usual intake on ordinary ones, and judge the result by your weekly average weight over three weeks.
Which activities burn the most, and does it matter?
Per hour, continuous vigorous activities such as running, fast cycling and swimming lead the table. Per week, the activity you will repeat wins. Three brisk 40-minute walks you never miss will do more than a punishing run you avoid.
- Walking costs little in fatigue and can be done every day; see daily steps.
- Steady endurance work at a conversational but challenging pace is the backbone; zone 2 heart rate explains how to set it.
- Strength training burns fewer calories per hour, but the ACSM position stand on weight loss found that it may increase fat-free mass and the loss of fat mass. It is part of any plan; see exercise to lose weight.
If you have a heart condition, high blood pressure, diabetes or a large amount of weight to lose, ask your doctor which intensity is right for you before chasing higher calorie numbers. Stop if you feel chest pain, faintness or unusual breathlessness.
Burn more by training more often, with Never Skip Club
The surest way to raise the calories you burn over a month is to miss fewer sessions. Create your free account on Never Skip Club, launch a guided workout of 20, 30 or 45 minutes at the gym, at home or in a hotel room, and join a crew of friends with a weekly rhythm: a session counts once it reaches 30 minutes, and the ranking rewards regularity. For a programme built around your goal, find a coach from our network, or sign in to pick up where you left off.
Questions
How many calories does 30 minutes of brisk walking burn?
For a person of 70 kilograms, the CDC gives about 140 kilocalories for 30 minutes of walking at 3.5 miles per hour, and about 230 at 4.5 miles per hour. A heavier person burns more, a lighter one less, roughly in proportion to body weight. Remember that part of this energy, about one MET, would have been used anyway at rest.
Are the calorie figures on fitness watches reliable?
Not very. In a Stanford study of seven wrist-worn devices tested against laboratory measurement, none estimated energy expenditure with an error below 20%, while most measured heart rate well. Errors were larger during walking and in people with a higher body mass index. Use the figure to compare weeks, not to decide what to eat.
Does lifting weights burn as many calories as cardio?
Usually fewer per hour. The CDC gives about 220 kilocalories an hour for a light weight-lifting workout and 440 for a vigorous one, against 590 for running at 5 miles per hour, for a person of 70 kilograms. Strength training earns its place differently: it helps preserve muscle and increase the share of fat in what you lose.
How do I convert a MET value into calories for my weight?
Multiply the MET value by your weight in kilograms, then by the duration in hours. The Compendium of Physical Activities defines one MET as about one kilocalorie per kilogram per hour. A 4 MET walk for an 85 kilogram person over one hour gives about 340 kilocalories, of which roughly 85 would have been used at rest.
Sources
- CDC: physical activity and your weight and health (calories per activity for a 70 kg person)
- Herrmann et al.: 2024 Adult Compendium of Physical Activities, a third update of the energy costs of human activities (J Sport Health Sci, 2024)
- Adult Compendium of Physical Activities: MET values and definitions
- Shcherbina et al.: accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure (J Pers Med, 2017)
- Pontzer et al.: constrained total energy expenditure and metabolic adaptation to physical activity in adult humans (Curr Biol, 2016)
- Mifflin et al.: a new predictive equation for resting energy expenditure (Am J Clin Nutr, 1990)
- American College of Sports Medicine: physical activity strategies for weight loss and prevention of weight regain (2009)