BMR Calculator
What is BMR?
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest - the energy your heart, brain, lungs and other organs need just to keep you alive. It is the largest piece of your daily calorie burn, usually 60-75% of the total.
Two quick profiles show the range. A 30-year-old man at 175 cm and 70 kg computes as 10 × 70 + 6.25 × 175 - 5 × 30 + 5, which lands at about 1,649 calories; his sedentary maintenance is roughly 1,979. A 30-year-old woman at 165 cm and 60 kg works out to 10 × 60 + 6.25 × 165 - 5 × 30 - 161, about 1,320 calories, with sedentary maintenance near 1,584. Notice what drives the gap: the difference in height and weight matters more than the formula's gender constant. Ten extra years of age would shave only about 50 calories from either result.
You only need four numbers. Enter your age, select gender, then provide height in centimeters and weight in kilograms - no activity questions, because BMR deliberately excludes movement. The calculator applies the Mifflin-St Jeor equation, the most widely recommended formula in clinical settings, and returns two figures: your BMR itself, and your sedentary maintenance, which multiplies BMR by 1.2 to cover a day with little or no exercise. That second number is the practical one - almost nobody spends 24 hours at true rest, so sedentary maintenance approximates a genuine minimum day.
BMR is most useful as a floor check. Dieters use it to avoid cutting calories so far that metabolism adapts and muscle suffers; clinicians use Mifflin-St Jeor as their default estimation formula; endurance athletes use it to confirm they are not chronically underfueled. Know its limits: it is an equation, not a measurement, typically accurate within about 10% and less reliable for very muscular or very high body-fat bodies. It also excludes digestion, exercise, cold, stress and caffeine, all of which raise real daily burn. If precision matters, a measured test such as indirect calorimetry beats any formula.
Frequently Asked Questions
What is the Mifflin-St Jeor equation?
For men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5. For women: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161. It estimates resting energy expenditure more accurately than older formulas like Harris-Benedict.
What is the difference between BMR and RMR?
BMR is measured under strict conditions (fasting, at rest, in a controlled environment). RMR (resting metabolic rate) is measured under less strict conditions and is usually slightly higher. Both are estimates of resting energy use; for practical purposes the difference is small.
How do I use my BMR to lose weight?
Your daily burn (TDEE) is your BMR times an activity factor, typically 1.2-1.9. To lose about 0.5 kg per week, eat roughly 500 calories below your TDEE - but do not chronically eat below your BMR, which can slow your metabolism.
Does BMR change with age?
Yes, mainly through body composition. Adults typically lose muscle gradually after 30, and the formula lowers BMR by about 50 calories per decade of age. Strength training slows much of that drift, which is why active older adults often burn more than the equation predicts for their age.
Does more muscle raise BMR?
Modestly. A kilogram of muscle contributes only about 13 calories per day at rest, so adding 5 kg of muscle raises BMR by roughly 65 calories - real, but not the huge boost often claimed. The bigger effect of training is the activity calories you burn while doing it.
Do I burn my BMR even when I sleep?
Yes - BMR covers unconscious housekeeping: heartbeat, breathing, body temperature, brain activity and cell repair. Sleep actually runs slightly below waking rest, which is why the formula assumes a resting but awake state. You burn it around the clock, on top of whatever movement you add.