Your basal metabolic rate (BMR) is one of three ways your body uses calories. It’s the number of calories your body needs to function at a basic level. Several factors influence your BMR, and the rate is different for everyone. Certain equations can help you estimate your BMR based on your sex, weight, height and age.
What Is Basal Metabolic Rate (BMR)? Your basal metabolic rate (BMR) refers to the minimum number of calories your body needs to function at a basic level. This includes maintaining all your cells and essential bodily functions, like breathing, blood circulation and body temperature. BMR varies from person to person based on several factors.
Your BMR is your body’s major source of energy expenditure. It fulfills 60% to 70% of the total energy your body uses. Your body uses about 10% of its total energy to process food into fuel. The remaining energy fuels your physical movement.
You may want to learn more about BMR to help manage your weight. It can help provide a general understanding of what your body needs to function. But know that your BMR is just one piece of the puzzle when it comes to weight management and calorie usage.
What is basal metabolic rate (BMR)? BMR is the minimum number of calories your body needs at complete rest to power essential functions like breathing, circulation, temperature regulation, and cell repair. Think of it as your metabolism’s baseline — the largest slice of your daily energy “budget.”
For most adults, BMR accounts for roughly 60–75% of total daily energy expenditure (TDEE) The rest comes from movement (exercise and non-exercise activity) and the thermic effect of food (the energy used to digest and process what you eat) BMR vs RMR (and why it matters) BMR is measured under strict lab conditions (fasted, thermoneutral environment, complete rest). Resting metabolic rate (RMR) is similar but measured under less strict conditions and is typically a bit higher than BMR.
Most consumer calculators labeled “BMR” actually estimate RMR. That’s okay — use the number as your baseline and adjust with real-world data.
How to calculate BMR (with examples) Several validated equations estimate BMR/RMR using your age, sex, height, and weight. Here are the most useful options.
1) Mifflin–St Jeor (recommended for most adults) Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161 This equation is widely considered the most accurate for the general population and is the default for many dietitians and clinicians.
2) Revised Harris–Benedict Men: BMR = 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age + 88.362 Women: BMR = 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age + 447.593 Useful, but can slightly overestimate for some people compared to Mifflin–St Jeor.
3) Katch–McArdle (best if you know your body fat %) BMR = 370 + 21.6 × LBM(kg), where LBM = lean body mass LBM(kg) = weight(kg) × (1 − body fat %) Great for those with reliable body-composition data (e.g., DEXA).
Quick examples
Woman, 35 years, 70 kg, 165 cm (Mifflin–St Jeor): 10×70 + 6.25×165 − 5×35 − 161 = 700 + 1031.25 − 175 − 161 ≈ 1,395 kcal/day Man, 35 years, 85 kg, 180 cm (Mifflin–St Jeor): 10×85 + 6.25×180 − 5×35 + 5 = 850 + 1125 − 175 + 5 ≈ 1,805 kcal/day
Frequently Asked Questions Should I eat below my BMR? No. Your BMR is the minimum calories your body needs to maintain basic functions. Eating fewer calories than your BMR is not recommended. In fact, consuming below BMR can trigger your body to slow the metabolism and protect itself from perceived starvation.
What happens if I eat only my BMR? If you eat exactly your BMR calories and remain mostly inactive, you will roughly maintain your weight, not lose it. That’s because you’re covering just your baseline needs. However, this leaves essentially no extra energy for exercise or daily activities, which can be very difficult to sustain. Over time, if you do eat only at your BMR and try to be active, you may feel fatigued or unsatisfied. In practice, weight loss strategies focus on eating below TDEE (which includes activity calories), not simply at or below BMR.
What’s the difference between BMR and Resting Metabolic Rate? Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) are often used interchangeably, but they have subtle differences. BMR is the number of calories your body needs to perform its most basic functions (like breathing and cell repair) under very strict conditions—typically measured after 8 hours of sleep and 12 hours of fasting, in a temperature-controlled environment. RMR, on the other hand, is slightly less precise and easier to measure, accounting for the energy your body uses at rest but under more typical, relaxed conditions. In practice, RMR is usually a bit higher than BMR, but both are reliable indicators of how many calories your body burns at rest.