The average person burns roughly 1,400 to 1,700 calories a day just by existing. For women, the average sits around 1,410 calories per day; for men, it’s closer to 1,696. This is your basal metabolic rate, the energy your body spends on breathing, pumping blood, maintaining body temperature, and keeping your cells alive while you do absolutely nothing.
That number accounts for a surprisingly large share of the calories you burn in a day. For most people, simply staying alive represents 60% to 70% of total daily energy expenditure. The rest comes from physical activity and digesting food. In other words, even if you spent the entire day in bed, your body would still burn through the majority of its daily calorie budget.
Where Those Calories Actually Go
Your organs are the real calorie burners, not your muscles. The brain alone consumes about 20% of your resting calories despite making up only 2% of your body weight. Your liver and brain each burn roughly 200 to 240 calories per kilogram of tissue per day. The heart and kidneys are even more demanding, burning around 440 calories per kilogram daily. These four organs, which together weigh only about 4 to 5 pounds, account for a disproportionate share of the energy you spend at rest.
Skeletal muscle, by comparison, is relatively modest. A pound of muscle burns about 4.5 to 7 calories per day at rest. Fat tissue burns even less. The reason muscular people have higher metabolic rates isn’t that muscle is an incredible calorie furnace on its own. It’s that having more lean mass shifts your overall body composition in a direction that supports higher energy expenditure, and the organs of larger, more muscular bodies tend to work harder to maintain homeostasis.
How to Estimate Your Own Number
The most accurate formula currently recommended by the Academy of Nutrition and Dietetics is the Mifflin-St. Jeor equation. It uses your weight in kilograms, height in centimeters, and age in years:
- Men: (9.99 × weight) + (6.25 × height) − (4.92 × age) + 5
- Women: (9.99 × weight) + (6.25 × height) − (4.92 × age) − 161
For a 35-year-old woman who weighs 150 pounds (68 kg) and stands 5’5″ (165 cm), the math works out to roughly 1,370 calories per day. A 35-year-old man at 180 pounds (82 kg) and 5’10” (178 cm) lands around 1,740. These numbers represent what your body burns in a state of complete rest, not including any walking, fidgeting, or digesting.
Online BMR calculators use this same formula, so they’ll give you a reasonable ballpark. The gold standard for precision is indirect calorimetry, a test where you breathe into a device that measures your oxygen consumption. Some dietitians and sports medicine clinics offer it, but for most people, the equation gets close enough.
Why Your Number Differs From Someone Else’s
Several factors push your resting calorie burn higher or lower. Body size is the biggest one. A larger body has more tissue to maintain, more blood to pump, and more surface area losing heat. Taller and heavier people almost always have higher resting metabolic rates, regardless of fitness level.
Body composition matters too, though less dramatically than the fitness industry suggests. Swapping ten pounds of fat for ten pounds of muscle might only add 45 to 70 extra resting calories per day. That’s meaningful over months and years, but it won’t transform your metabolism overnight.
Age plays a steady, gradual role. Resting energy expenditure drops by roughly 4 calories per year even after adjusting for changes in body composition. That means between ages 30 and 60, you could be burning about 120 fewer calories per day at rest, independent of any muscle loss. The decline isn’t steep enough to notice year to year, but it accumulates.
Sex also creates a gap. Men tend to carry more lean mass and less body fat at any given weight, which partly explains why their average resting burn runs about 280 calories higher than women’s. Hormonal differences contribute as well, particularly testosterone’s effect on maintaining muscle tissue.
Things That Temporarily Shift Your Resting Burn
Cold exposure is one of the few environmental factors that meaningfully increases resting calorie burn. When researchers exposed people to mild cold (around 60 to 66°F), their energy expenditure rose by an average of about 188 calories per day compared to a comfortable room temperature. In people with more active stores of brown fat (a type of fat tissue that generates heat), resting metabolic rate increased by about 14% during cold exposure. This isn’t a weight loss strategy, but it illustrates how your body ramps up energy use to maintain its core temperature.
Illness and fever also spike resting metabolism. Your immune system is energetically expensive to run, and body temperature increases raise calorie burn by roughly 7% for every degree Fahrenheit above normal. Sleep deprivation, stress, and hormonal shifts (particularly thyroid hormones) can nudge the number in either direction, though these effects vary widely between individuals.
Caffeine and spicy food produce small, temporary bumps in metabolic rate, but the effect is modest, typically in the range of 3% to 10% for a few hours. Over a full day, that might translate to 30 to 80 extra calories, depending on the dose and your sensitivity.
Resting Metabolism vs. Total Daily Burn
Your resting metabolic rate is only one piece of the puzzle. On top of it, your body spends about 10% of daily calories on the thermic effect of food, which is the energy required to digest, absorb, and process what you eat. Physical activity adds the rest, and this is the most variable component. A sedentary office worker might add only 200 to 400 calories through daily movement, while someone with a physically demanding job or regular exercise habit could add 800 or more.
For a rough total, multiply your resting metabolic rate by an activity factor: 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, and 1.725 for very active. Using the earlier example of a woman with a resting rate of 1,370 calories, a sedentary day would bring her total to about 1,644, while a moderately active day would land around 2,124. The calories you burn just existing form the floor. Everything else stacks on top.