Your body burns between 1,400 and 2,500 calories per day before any intentional exercise, depending on your size, age, sex, and how much you move around in daily life. Most of that burn happens without you doing anything at all. Understanding where those calories go can help you make smarter decisions about eating and activity.
The Three Ways Your Body Burns Calories
Your total daily energy expenditure breaks down into three main categories: your basal metabolic rate (the calories you burn just staying alive), the energy it takes to digest food, and the calories burned through all forms of physical activity. Each one contributes a different share.
Basal metabolic rate, or BMR, is the biggest piece. In people with mostly sedentary jobs, it accounts for roughly 60% of all the calories burned in a day. This is the energy your body needs to keep your heart beating, your lungs breathing, your brain running, and your cells functioning while you do absolutely nothing.
Digesting food takes energy too, a process called the thermic effect of food. This typically accounts for 8 to 15% of your total daily burn. The rest comes from physical activity, which includes everything from formal exercise to fidgeting, walking to your car, and standing at your desk.
What Your Body Burns at Rest
Even if you stayed in bed all day, your organs would still be working hard. The heart and kidneys are the most metabolically expensive tissues in the body, each burning about 440 calories per kilogram per day. The brain burns around 240 calories per kilogram daily, and the liver uses about 200. Skeletal muscle, despite making up a much larger share of your body weight, burns only about 13 calories per kilogram per day at rest.
This is why the common claim that “muscle burns 50 calories per pound” is exaggerated. The real number is closer to 5 to 7 calories per pound per day. That still matters over time, since muscle contributes about 20% of your total daily energy expenditure compared to just 5% from fat tissue (in someone with around 20% body fat). But adding a few pounds of muscle won’t dramatically transform your metabolism overnight.
Your resting metabolic rate declines with age, losing roughly 4 calories per year even after accounting for changes in body composition. Muscle atrophy begins around age 25 and accelerates over the decades, which partially explains why older adults burn fewer calories. Between ages 40 and 66, both men and women tend to gain 0.3 to 0.5 kg per year on average, in part because of this slow metabolic decline.
How Food Choices Affect Your Burn
Not all calories cost the same amount of energy to digest. Protein has the highest thermic effect by far: your body uses 20 to 30% of the calories in protein just to break it down and absorb it. Carbohydrates cost 5 to 10%, and fat costs the least at 0 to 3%. So eating 200 calories of chicken breast requires your body to spend 40 to 60 of those calories on digestion, while 200 calories of butter costs almost nothing to process.
This doesn’t mean you should eat nothing but protein, but it does explain part of why higher-protein diets tend to slightly increase overall calorie burn throughout the day.
Exercise vs. Everyday Movement
Formal exercise (running, weight training, cycling) can account for 15 to 30% of your total daily burn if you train regularly. But for most people, the bigger variable is non-exercise activity thermogenesis, or NEAT. This includes everything from cooking dinner to pacing during a phone call to tapping your foot under the desk.
In sedentary people, NEAT accounts for just 6 to 10% of total daily calories burned. In highly active people, especially those with physically demanding jobs, it can reach 50% or more. That gap can easily represent several hundred calories per day, which is why small habits like taking stairs, walking during breaks, and standing more often add up significantly over weeks and months.
Calories Burned During Common Activities
Exercise intensity is measured in METs, or metabolic equivalents. One MET equals the energy you burn sitting quietly. An activity rated at 7 METs burns seven times that amount. To estimate calories per hour, multiply the MET value by your weight in kilograms. A 70 kg (154 lb) person would burn roughly 245 calories per hour walking briskly at 3.5 mph (4.3 METs), about 490 calories per hour jogging (7.0 METs), and around 560 calories per hour doing vigorous circuit training (8.0 METs).
- Moderate walking (2.8 to 3.2 mph): 3.5 METs
- Brisk walking (3.5 mph): 4.3 METs
- Jogging: 7.0 METs
- Vigorous circuit training or HIIT: 8.0 METs
The heavier you are, the more calories you burn doing the same activity. A 90 kg person jogging burns about 630 calories per hour, while a 60 kg person burns about 420.
How to Estimate Your Daily Burn
The most widely recommended formula for estimating your resting calorie burn is the Mifflin-St. Jeor equation. In a recent study comparing multiple prediction formulas against laboratory measurements, it tied for the highest accuracy rate at 73%, making it one of the most reliable options available without clinical testing.
The formula works like this:
- Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
This gives you your resting metabolic rate in calories per day. To estimate your total daily burn, multiply by an activity factor: 1.2 for sedentary, 1.375 for lightly active (light exercise 1 to 3 days per week), 1.55 for moderately active, and 1.725 for very active. For a 30-year-old woman who weighs 65 kg (143 lbs), stands 165 cm (5’5″), and exercises a few times a week, that works out to roughly 1,370 calories at rest and about 1,880 total per day.
Why Your Number Might Differ
These formulas give useful estimates, but individual variation is real. Thyroid hormones play a measurable role in setting your metabolic rate, even when thyroid function falls within the normal range. People at the higher end of normal thyroid activity tend to burn slightly more at rest than those at the lower end, without any diagnosable thyroid condition.
Sleep, stress, and body composition also shift the number. Two people with the same height, weight, age, and sex can have resting metabolic rates that differ by 200 to 300 calories per day. Genetics, hormone levels, and the ratio of muscle to fat all contribute to this gap. If calorie estimates from formulas don’t seem to match your real-world experience with weight gain or loss, the formula isn’t wrong per se, it’s just working with incomplete information about your specific body.