A metabolic equivalent, or MET, is a unit that describes how much energy your body uses during a given activity compared to sitting quietly at rest. One MET equals 3.5 milliliters of oxygen consumed per kilogram of body weight per minute, which is roughly the energy cost of sitting in a chair doing nothing. An activity rated at 4 METs, like brisk walking, means your body is burning four times that resting amount. It’s a simple, standardized way to compare the intensity of virtually any physical activity on one scale.
How the MET Scale Works
The idea behind METs is straightforward: your body burns energy all the time, even at rest. That baseline resting rate is 1 MET. Every physical activity gets a number reflecting how many times harder your body works compared to that baseline. Walking slowly around your house comes in around 2 METs (twice resting effort), while jogging lands near 8 METs (eight times resting effort).
These values come from the Compendium of Physical Activities, a standardized reference developed for researchers studying the link between physical activity and health outcomes. It assigns a MET value to hundreds of specific activities so that scientists, clinicians, and fitness professionals are all speaking the same language when they talk about exercise intensity. The concept dates back to the work of physiologist Bruno Balke, who proposed using the fixed resting oxygen consumption of 3.5 mL/kg/min as a simple denominator for expressing the energy cost of movement.
Intensity Categories by MET Value
Health organizations group physical activities into bands based on their MET rating:
- Sedentary: 1.5 METs or fewer. Sitting, lying down, watching TV.
- Light intensity: 1.6 to 3.0 METs. Slow walking, light housework, casual stretching.
- Moderate intensity: 3.0 to 6.0 METs. Brisk walking (about 4 METs), cycling at a relaxed pace, gardening.
- Vigorous intensity: 6.0 METs and above. Jogging (about 8 METs), shoveling heavy soil (8.5 METs), running, competitive sports.
These categories are the basis for public health exercise recommendations. When the World Health Organization advises 150 to 300 minutes per week of moderate-intensity activity, or 75 to 150 minutes of vigorous activity, the distinction between “moderate” and “vigorous” is drawn at that 6-MET line. You can also mix the two: a minute of vigorous activity counts roughly as two minutes of moderate activity because you’re burning energy at a proportionally higher rate.
Estimating Calories Burned With METs
One MET is approximately equal to 1 kilocalorie burned per kilogram of body weight per hour. That gives you a simple formula for estimating calorie expenditure during any activity:
Calories burned per hour = MET value × your weight in kilograms
So a 70 kg person (about 154 pounds) brisk walking at 4 METs would burn roughly 280 calories per hour (4 × 70). The same person jogging at 8 METs would burn about 560 calories per hour. To convert your weight from pounds to kilograms, divide by 2.2.
This estimate is useful for comparing activities and planning workouts, but it’s an approximation. Your actual calorie burn depends on factors like fitness level, body composition, and how efficiently you move. Still, it’s one of the most practical tools available for putting a number on how hard different activities work your body.
METs in Medical Settings
Beyond fitness tracking, METs play a significant role in cardiology. During a treadmill stress test, the peak MET level you achieve is one of the strongest predictors of your long-term cardiovascular risk. Research has found that each 1-MET increase in peak exercise capacity is associated with a 13% reduction in all-cause mortality and a 15% reduction in heart disease events.
Patients who reach 10 METs or higher on a stress test have an excellent prognosis over years of follow-up, with very low rates of cardiac death and heart attack, regardless of their peak heart rate during the test. In fact, peak exercise capacity measured in METs has been shown to be a better predictor of mortality than peak heart rate itself, both in people with and without known heart disease. A large analysis found that people with a maximum capacity of about 8 METs or higher had substantially lower event rates compared to those who fell below that threshold.
This is why your cardiologist cares about how many METs you can sustain. It’s not just a fitness number. It’s a window into how well your cardiovascular system functions under demand, and it helps guide decisions about further testing, treatment intensity, and activity recommendations after a cardiac event.
Why the Standard MET Isn’t Perfect for Everyone
The 3.5 mL/kg/min value that defines 1 MET was derived from a reference person: a 40-year-old man weighing about 70 kg. In practice, resting metabolic rate varies considerably from person to person. Age, sex, body composition, and fitness level all influence how much oxygen your body actually consumes at rest.
Body composition shifts meaningfully over a lifetime. Lean muscle mass, which is the most metabolically active tissue in the body, tends to decline after age 55 in men and after age 31 in women. Fat mass generally increases with age in both sexes, though in women it tends to plateau and decrease after about age 75. Resting energy expenditure, adjusted for lean mass, begins declining around age 46 to 47. All of this means the “1 MET = 3.5 mL/kg/min” assumption overestimates resting metabolism for older adults and people with less muscle mass, and underestimates it for highly muscular or younger individuals.
For most practical purposes, like choosing activities, comparing exercise options, or hitting weekly activity goals, the standard MET values work well enough. But if you’re using them to calculate precise calorie counts, treat the result as a ballpark rather than an exact figure. The real value of METs is in relative comparison: knowing that jogging is roughly twice as demanding as brisk walking, or that your stress test score improved from 7 to 9 METs over a year of training. Those relative differences hold up even when the absolute resting baseline isn’t a perfect match for your body.