Most adults burn between 1,300 and 2,000 calories a day doing absolutely nothing. That range covers the energy your body spends just keeping you alive: pumping blood, breathing, regulating temperature, and maintaining billions of cells. Your exact number depends on your size, age, sex, and body composition.
What “Calories Burned at Rest” Actually Means
Two terms describe resting calorie burn, and they’re nearly interchangeable for everyday purposes. Your basal metabolic rate (BMR) is the absolute minimum energy your body needs to function, measured under strict lab conditions after a 12- to 14-hour fast while you’re completely still, awake, and in a temperature-controlled room. Your resting metabolic rate (RMR) is a slightly more practical number that includes the calories needed for very low-effort activities like getting out of bed or walking to the bathroom. RMR runs about 10% higher than BMR.
When people ask “how many calories do I burn resting,” they’re usually asking about RMR. Either way, this baseline metabolism accounts for the largest share of your daily calorie burn, typically 60% to 75% of everything you use in a day.
Average Resting Calories by Age and Sex
Using the average body size for U.S. adults (5’9″ and 199 lbs for men, 5’3.5″ and 172 lbs for women), here’s what resting calorie burn looks like across the lifespan:
- Age 20: ~2,025 calories (men) / ~1,581 calories (women)
- Age 30: ~1,968 calories (men) / ~1,538 calories (women)
- Age 40: ~1,912 calories (men) / ~1,495 calories (women)
- Age 50: ~1,855 calories (men) / ~1,451 calories (women)
- Age 60: ~1,798 calories (men) / ~1,408 calories (women)
- Age 70: ~1,741 calories (men) / ~1,365 calories (women)
- Age 80: ~1,685 calories (men) / ~1,321 calories (women)
These numbers are estimates based on a commonly used formula, so your personal number could be higher or lower depending on how much muscle you carry, your genetics, and your hormonal health. Still, they give you a solid ballpark. If you’re smaller than the averages listed above, expect a lower BMR. If you’re larger, expect a higher one.
How to Estimate Your Own Number
The most widely recommended formula for estimating resting metabolic rate is the Mifflin-St Jeor equation. A systematic review in the Journal of the American Dietetic Association found it predicted resting metabolism within 10% of the lab-measured value in more people, both at a healthy weight and with obesity, than any other common formula. It also had the narrowest margin of error.
The formula uses your weight in kilograms, height in centimeters, and age in years:
- Men: (10 × weight) + (6.25 × height) – (5 × age) + 5
- Women: (10 × weight) + (6.25 × height) – (5 × age) – 161
To convert: divide your weight in pounds by 2.2 for kilograms, and multiply your height in inches by 2.54 for centimeters. Plenty of online calculators will do the math for you. Keep in mind that no formula is perfect for every individual, and the Mifflin-St Jeor equation can be less accurate for older adults and certain ethnic groups.
If you want a truly precise measurement, some clinics and sports medicine facilities offer indirect calorimetry. You lie still while a clear plastic hood is placed over your head, and a machine measures exactly how much oxygen you consume and how much carbon dioxide you produce. Your calorie burn is then calculated from that gas exchange. It takes about 15 to 30 minutes and gives you a personalized number rather than a formula-based estimate.
Why Some People Burn More at Rest
Body size is the single biggest factor. A larger body has more tissue to maintain, so it burns more calories at rest. But several other variables shift the number significantly.
Muscle vs. fat. Muscle tissue is more metabolically active than fat, but the difference is often exaggerated. Researchers at the University of New Mexico estimate that muscle burns roughly 4.5 to 7 calories per pound per day, while the old gym-floor claim of 50 calories per pound has no real evidence behind it. Still, muscle contributes about 20% of total daily calorie burn compared to roughly 5% for fat tissue in someone with average body composition. Adding muscle does increase your resting metabolism, just not as dramatically as many fitness sources suggest.
Sex. Men tend to have a higher resting metabolic rate primarily because they carry more muscle mass and less body fat on average. The hormonal differences between men and women also play a role, with testosterone supporting greater lean mass.
Thyroid function. Your thyroid gland acts like a thermostat for metabolism. When it produces too much hormone (hyperthyroidism), your resting calorie burn rises. When it underproduces (hypothyroidism), your BMR drops. If your resting metabolism seems unusually low or high relative to your size, thyroid function is one of the first things worth checking.
Genetics. Some of the variation between people of the same size, age, and sex comes down to inherited differences in how efficiently their cells convert fuel into energy. This isn’t something you can change, but it helps explain why two people with identical stats might have noticeably different resting calorie burns.
How Aging Affects Resting Metabolism
The conventional wisdom says your metabolism starts slowing in your 30s and drops steadily from there. A large-scale study published in Science and covered by Harvard Health challenged that idea. Researchers found that both total energy expenditure and basal metabolic rate stay remarkably stable between ages 20 and 60, regardless of sex. The midlife weight gain most people experience appears to be driven more by changes in activity and eating habits than by a metabolic slowdown.
The real decline begins around age 60. From that point, resting metabolism drops by about 0.7% per year, even after accounting for changes in body size. By age 90 and beyond, adjusted total energy expenditure is roughly 26% below that of middle-aged adults. Part of this decline tracks with the gradual loss of lean muscle mass that accelerates in later decades, but the research suggests metabolism slows beyond what muscle loss alone would explain.
What This Means for Weight Management
Your resting calorie burn sets the floor for your daily energy needs. Everything you do on top of existing, from walking to the kitchen to running a marathon, adds to this baseline. So if your BMR is 1,600 calories and you lead a moderately active life, your total daily burn might land somewhere around 2,200 to 2,400 calories.
Knowing your approximate resting metabolism helps you set realistic calorie targets. Eating significantly below your BMR for extended periods can trigger adaptive responses where your body becomes more efficient and burns fewer calories, making sustained weight loss harder. This is one reason very low-calorie diets often backfire over time.
The most reliable way to nudge your resting metabolism upward is to build and maintain muscle through resistance training. The calorie increase per pound of muscle is modest, but it compounds over your whole body and provides long-term metabolic benefits that go well beyond the numbers on a calculator. Staying physically active also helps preserve lean mass as you age, counteracting the natural decline that kicks in around 60.