Most people burn roughly 60 to 70 calories per hour at complete rest. During exercise, that number can climb to 400, 600, or more depending on the activity, your body weight, and how hard you push. The exact figure varies from person to person, but a simple formula lets you estimate your own.
Your Baseline: Calories Burned at Rest
Even when you’re doing absolutely nothing, your body spends energy keeping your heart beating, your lungs breathing, and your cells functioning. This baseline is called your basal metabolic rate (BMR). The average adult male burns about 1,696 calories per day at rest, which works out to roughly 71 calories per hour. The average adult female burns about 1,410 calories per day at rest, or roughly 59 calories per hour.
Sleep drops you slightly below that baseline. During sleep your body temperature falls, your muscles relax, and your brain activity decreases, bringing your hourly burn down to approximately 50 calories. Simply standing instead of sitting nudges the number up because your postural muscles engage to keep you upright, adding a modest bump of 10 to 20 extra calories per hour compared to sitting.
Calorie Burn for Common Activities
Mayo Clinic data for a 160-pound (73 kg) person gives a useful snapshot of what one hour of different activities costs in energy:
- Running at 5 mph: 606 calories
- Hiking: 438 calories
- Swimming laps (light to moderate): 423 calories
- Water aerobics: 402 calories
- Low-impact aerobics or elliptical (moderate effort): 365 calories
Walking is at the lower end. A slow walk of 1 to 2 mph on a treadmill burns in the range of 150 to 200 calories per hour for the same 160-pound person. That’s still roughly triple your resting rate, which makes even a casual stroll meaningful over the course of a week.
How to Estimate Your Personal Number
Researchers assign every physical activity a MET value, short for metabolic equivalent. One MET equals the energy you burn sitting quietly, which is about 1 calorie per kilogram of body weight per hour. An activity rated at 5 METs burns five times as much energy as sitting still.
The formula is straightforward: multiply the MET value of the activity by your weight in kilograms, then multiply by the number of hours. For example, if you weigh 80 kg (about 176 pounds) and go for a run rated at 8 METs for 30 minutes (0.5 hours), the math looks like this: 8 × 80 × 0.5 = 320 calories. To convert your weight from pounds to kilograms, divide by 2.2.
This formula gives a reasonable estimate, though individual variation in fitness level, genetics, and body composition will shift the real number up or down by 10 to 15 percent.
Why Body Weight Matters So Much
Your body weight is the single biggest lever on calorie burn during any activity. A heavier person moves more mass with every step, stroke, or pedal rotation, and that takes more energy. The same 5 mph run that burns 606 calories for a 160-pound person will burn noticeably more for someone at 200 pounds and less for someone at 130 pounds. Using the MET formula, a 200-pound person running at 8 METs for one hour burns roughly 727 calories, while a 130-pound person burns about 473.
Body composition plays a role too, though it’s smaller than many people assume. A pound of muscle burns roughly 5 to 7 calories per day at rest. A pound of fat burns considerably less, closer to 1 to 2 calories per day. Your internal organs, including your brain, liver, and kidneys, actually account for a much larger share of resting metabolism. Organ tissue burns 15 to 40 times more energy per unit of weight than muscle does. So while building muscle does increase your resting calorie burn, it takes a substantial amount of added muscle to make a noticeable daily difference.
Age and Metabolism: Not What You Think
A widely held belief is that metabolism crashes after your 30s, making it easier to gain weight with each passing decade. A large-scale study published in Science and covered by Harvard Health found something different. Basal metabolic rate stays remarkably stable from age 20 all the way to 60 when adjusted for body composition. The gradual weight gain many people experience in their 30s and 40s is driven more by changes in activity level and eating habits than by a meaningful metabolic slowdown. After 60, metabolism does begin to decline, but even then the drop is gradual, roughly 0.7 percent per year.
Temperature and Environment
Exercising in extreme cold or heat forces your body to spend extra energy on temperature regulation. In cold environments, your muscles shiver and your body ramps up heat production, which increases calorie expenditure both during and after exercise. In hot environments, the picture is more nuanced: your body actually tends to reduce both energy intake and expenditure to avoid generating additional internal heat. The practical difference for most people exercising in a heated gym or on a chilly morning jog is relatively small, maybe 5 to 10 percent in either direction. You’d need prolonged, genuine cold exposure (think cold-water swimming or extended winter hiking) to see a substantial bump.
The Afterburn Effect
After a hard workout, your body continues burning extra calories as it restores oxygen levels, repairs tissue, and clears metabolic byproducts. This post-exercise calorie burn, often called the “afterburn effect,” can last anywhere from 3 to 24 hours after intense exercise. However, the extra calories are modest. Research shows the afterburn typically adds only 6 to 15 percent on top of whatever you burned during the workout itself. So if you burned 400 calories running, you might burn an additional 25 to 60 calories over the following hours.
Getting a meaningful afterburn requires serious effort: at least 50 minutes at 70 percent or more of your maximum capacity, or shorter all-out intervals above your aerobic threshold. For most people, the calories burned during the workout itself matter far more than what happens afterward. The afterburn is a nice bonus, not a weight-loss strategy on its own.