BMR Calculator
Find your Basal Metabolic Rate — the calories your body burns just to keep you alive at complete rest.
How this calculator works
This uses the Mifflin-St Jeor equation, considered one of the most accurate BMR formulas for the general population.
W = weight in kg · H = height in cm · A = age in years
BMR vs. total daily energy expenditure
BMR is just your resting energy use — it doesn't include activity. Multiply BMR by an activity factor (roughly 1.2 to 1.9) to estimate your total daily calorie needs, which is what the two figures below show as rough bounds. For a more precise activity-adjusted number, use our TDEE Calculator.
BMR changes over your lifetime
BMR generally decreases with age, partly due to natural muscle loss over time (since muscle burns more calories at rest than fat tissue) — this is one reason calorie needs often decrease gradually as people get older even without weight changes.
Maintaining muscle mass through resistance training is one of the few practical ways to help offset this natural age-related decline in BMR, since muscle tissue burns more calories at rest than fat.
A worked example
A 28-year-old woman, 65kg, 165cm: BMR works out to 10 times 65 plus 6.25 times 165 minus 5 times 28 minus 161, which equals 650 plus 1,031 minus 140 minus 161, or 1,380 calories/day at complete rest.
At a sedentary activity level (times 1.2), her estimated daily calorie needs would be about 1,656; at a very active level (times 1.725), that rises to roughly 2,381 — a difference of over 700 calories purely from activity level.
Factors that influence your BMR beyond this formula
While the Mifflin-St Jeor equation used here is one of the most accurate general-purpose formulas, individual BMR can vary due to genetics, muscle mass, hormone levels (including thyroid function), and even body temperature regulation — meaning your actual BMR could differ somewhat from the formula's estimate.
Muscle mass is one of the more controllable factors — since muscle tissue burns more calories at rest than fat tissue, building and maintaining muscle through strength training can meaningfully raise your BMR over time.
Frequently asked questions
What's the difference between BMR and calorie needs?
BMR is the energy used at complete rest. Your actual daily calorie needs (TDEE) are higher because they include movement, exercise, and digestion.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation used here is generally considered more accurate than the older Harris-Benedict equation for most adults.
Can I increase my BMR?
Building muscle through resistance training is the most reliable way to meaningfully raise BMR over time, since muscle tissue burns more calories at rest than fat tissue does.
Is the Mifflin-St Jeor formula the most accurate?
It's widely considered one of the more accurate general-population formulas available, though individual metabolism can still vary from any formula's prediction by a meaningful margin.
Can I increase my BMR?
Building muscle through strength training is one of the more reliable ways to raise resting metabolic rate over time, since muscle tissue burns more calories at rest than fat tissue.
How much does BMR typically decline with age?
BMR tends to decline gradually with age, partly due to natural muscle loss over time — maintaining muscle mass through strength training can help offset this decline.