Calories Burned by Activity: How METs Work

Fitness trackers and gym machines love to tell you how many calories you just burned, but where do those numbers come from? Behind most estimates is a simple, well-established concept called the MET. Understanding how METs work lets you sanity-check any device and roughly estimate the energy cost of almost any activity, from a slow walk to a hard bike ride.

What Is a MET?

MET stands for metabolic equivalent of task. One MET is defined as the amount of energy you use while sitting quietly at rest. By convention, that resting rate is about 3.5 milliliters of oxygen per kilogram of body weight per minute, which works out to roughly 1 calorie per kilogram of body weight per hour.

Every activity is assigned a MET value that describes how much harder it makes your body work compared to rest:

• A 2 MET activity burns energy about twice as fast as resting.
• A 5 MET activity burns energy about five times as fast as resting.
• A 10 MET activity burns energy about ten times as fast as resting.

These values come from a research reference called the Compendium of Physical Activities, which catalogs hundreds of activities and is widely used by exercise scientists and public health agencies. Health authorities also group activities by intensity: moderate-intensity activity generally falls in the 3 to under 6 MET range, and vigorous-intensity activity is 6 METs or higher.

The Formula for Estimating Calories

You can estimate the calories burned during an activity with one straightforward equation:

Calories per minute = MET × 3.5 × body weight in kilograms ÷ 200

To get the total for a session, multiply that by the number of minutes. Here is a worked example for a 70 kg (about 154 lb) person doing a 6 MET activity, such as a brisk cycling effort, for 30 minutes:

• Calories per minute = 6 × 3.5 × 70 ÷ 200 = about 7.4 calories.
• Over 30 minutes = 7.4 × 30 = about 220 calories.

Notice two things this formula makes obvious. First, a heavier person burns more calories doing the same activity, because there is more mass to move. Second, both the intensity (the MET value) and the duration matter, so a longer, easier session can burn as much as a shorter, harder one.

MET Values for Common Activities

Approximate MET values give you a feel for how activities compare. Actual numbers vary with pace, terrain, technique, and fitness, so treat these as ballpark figures:

• Sitting or light desk work: about 1.3 to 1.5 METs
• Slow walking, around 2 mph: about 2.8 METs
• Brisk walking, around 3.5 mph: about 4.3 METs
• General light housework: about 2.5 to 3.5 METs
• Recreational swimming: about 6 METs
• Jogging, general: about 7 METs
• Running at 6 mph (10-minute mile): about 9.8 METs
• Vigorous cycling, 14 to 16 mph: about 10 METs
• Jumping rope, moderate pace: about 10 to 12 METs

Why Real-World Numbers Vary

MET-based estimates are useful, but they are averages drawn from groups of people. Your actual burn depends on individual factors that a simple formula cannot fully capture:

• Body composition: muscle is more metabolically active than fat, so two people of the same weight can burn slightly different amounts.
• Fitness level: a well-trained person may move more efficiently, sometimes using less energy for the same task.
• Environment: heat, cold, wind, hills, and altitude all change the effort involved.
• Effort and technique: "cycling" or "swimming" covers a huge range of intensities, and the MET value assumes a specific pace.

This is also why wearable devices and cardio machines often disagree with each other. Wrist-based heart rate and step estimates involve their own assumptions, and studies have found that consumer trackers can be reasonably good at estimating heart rate but noticeably less accurate at estimating calories, sometimes off by 20 to 30 percent or more. Use these numbers to compare your own workouts over time rather than as precise accounting.

Putting METs to Use

You do not need to memorize equations to benefit from the concept. A few practical uses:

• Use MET intensity bands to meet activity goals. The U.S. Physical Activity Guidelines recommend that adults get at least 150 to 300 minutes of moderate-intensity, or 75 to 150 minutes of vigorous-intensity, aerobic activity per week, plus muscle-strengthening activities on two or more days.
• Swap the "talk test" for MET math when you are exercising: during moderate activity you can talk but not sing, while during vigorous activity you can only say a few words before pausing for breath.
• Trade intensity for time when you need to. A shorter vigorous session can meet the same weekly goal as a longer moderate one.

A Note on Health and Safety

Calorie-burn figures are estimates for general fitness planning, not medical measurements. If you have heart disease, high blood pressure, diabetes, joint problems, are pregnant, or have been inactive for a long time, talk with your doctor before starting or significantly increasing an exercise program. Stop and seek medical attention if you experience chest pain, severe shortness of breath, dizziness, or faintness during activity.

The Takeaway

A MET tells you how hard an activity is compared to sitting still, and a single formula, MET × 3.5 × your weight in kilograms ÷ 200, gives a reasonable per-minute calorie estimate. Heavier bodies and higher intensities burn more, but every number is an approximation. Focus on hitting the recommended weekly activity totals and on your own trends over time, and check with a healthcare professional before ramping up if you have any health concerns.