BMR Calculator — Basal Metabolic Rate
Find your Basal Metabolic Rate — the calories your body burns just to keep you alive at complete rest. Compare four published formulas, see your hourly resting burn, and how your BMR is likely to change with age.
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How Your BMR Changes With Age
Mifflin-St Jeor at your current weight and height — the formula lowers BMR by 5 kcal a day for each year of age.
| Age | BMR | Per Hour | vs Today |
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How this calculator works
This uses the Mifflin-St Jeor equation, a widely used general-population predictive equation. No BMR equation is universally most accurate for every person.
Men: 10W + 6.25H − 5A + 5 · Women: 10W + 6.25H − 5A − 161 — W = weight in kg · H = height in cm · A = age in years
For comparison it also shows the revised Harris-Benedict equation (Roza & Shizgal, 1984) and, if you enter your body-fat percentage, the lean-mass-based Katch-McArdle (370 + 21.6 × LBM) and Cunningham (500 + 22 × LBM) equations.
By Suhaib Hassan · Reviewed 28 September 2026 against the original published equations · How CalculatePilot verifies formulas →
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 range above shows 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 may help preserve resting energy expenditure as body composition changes with age, although individual changes vary.
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 is widely used for general-purpose estimation, individual resting energy expenditure 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. Medical information, not medical advice.
Sources
- Mifflin et al. (1990), A new predictive equation for resting energy expenditure — PubMed
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr 1984;40:168–182.
- Cunningham JJ. A reanalysis of the factors influencing basal metabolic rate in normal adults. Am J Clin Nutr 1980;33:2372–2374.
- Mayo Clinic Calorie Calculator
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?
Mifflin-St Jeor is widely used and performs well in validation studies, but no predictive BMR equation is universally most accurate for every person.
Is the Mifflin-St Jeor formula the most accurate?
It is a widely used general-population equation, but any formula is an estimate and individual energy needs can differ meaningfully from the prediction.
Can I increase my BMR?
Increasing or preserving lean mass can affect resting energy expenditure, but the size of the change varies between people; strength training is useful for maintaining muscle and overall fitness, not a guarantee of a specific BMR increase.
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.
Next Steps
Add activity and goals to your resting burn.