BMR Calculator: Basal Metabolic Rate
Estimate the calories your body burns at complete rest, using three published equations.
- 2 cited sources
- Calculates in your browser
Your answer
Appears here as you enter your details. No demo figures — the number is yours, or it is nothing.
Baseline
Know all your numbers
BMI, resting rate, daily burn, eating target, macros, body fat, waist ratios, heart-rate zones and your fitness age: 15 in all. Answer once, see them together, and stop whenever you like.
Get my Baseline →Methodology
Three published equations estimate basal metabolic rate here. The default
is Mifflin-St Jeor (men 10W + 6.25H − 5A + 5; women
10W + 6.25H − 5A − 161, with weight in kg, height in cm, age in years),
repeatedly found the most reliable general-purpose prediction equation.
Katch-McArdle (370 + 21.6 × fat-free mass) works from lean mass when
you can supply a measured body-fat percentage, and the revised
Harris-Benedict (Roza & Shizgal, 1984) is included for comparison with
older references.
Interpreting your result
BMR is the energy cost of simply existing (organ function, cell turnover, temperature regulation) measured at complete rest. It is not the number to eat to: real days include movement, digestion and exercise, which is what the TDEE calculator adds on top. Prediction equations typically land within about 10% of laboratory measurement for healthy adults; muscular people run higher than predicted and very sedentary people lower.
Limitations
- All three equations describe population averages; individual metabolisms legitimately vary around them.
- Katch-McArdle inherits every error in your body-fat estimate.
- BMR falls as you diet (adaptive thermogenesis), so recalculate after meaningful weight change.
- Suspected thyroid or metabolic issues are a matter for your GP, not a calculator.
Sources
Pull the receipts, 2 cited sources
FitTools · sources
- 01 Mifflin MD, St Jeor ST, et al. Am J Clin Nutr 1990;51:241-247
- 02 Roza AM, Shizgal HM. Am J Clin Nutr 1984;40:168-182
Every formula cited ✓
Frequently asked questions
- What is BMR?
- Basal metabolic rate is the energy your body uses at complete rest for basic functions such as breathing, circulation and cell maintenance. It typically makes up 60 to 75% of the calories most people burn in a day.
- What is the difference between BMR and TDEE?
- BMR is resting energy only; TDEE multiplies it by an activity factor to estimate your full daily burn. Use TDEE for calorie planning, and BMR to understand the baseline underneath it.
- Which BMR formula is most accurate?
- Mifflin-St Jeor is the best validated for most adults and is the default here. Katch-McArdle can edge ahead if you know your body-fat percentage from a reliable measurement.
- Can I eat below my BMR?
- Eating below BMR is not automatically dangerous, but it usually signals an overly aggressive deficit. Sustainable fat-loss targets sit between BMR and TDEE, and large deficits deserve professional supervision.
Related tools
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A free account puts this number on a home screen with the rest of yours, on every device you sign in on. One tap, no password.
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A target is easier to hit when something counts for you. Free food diary in your browser, with barcode scanning and the source of every number on show.
- TDEE Calculator: Total Daily Energy Expenditure
Estimate your total daily energy expenditure (TDEE) and BMR with the Mifflin-St Jeor, Katch-McArdle or revised Harris-Benedict equations. Free, no sign-up.
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Free macro calculator: protein by bodyweight (1.6 to 2.2 g/kg, per Morton 2018), your chosen fat percentage, and gram and calorie targets for each macro.
- Lean Body Mass Calculator: Boer Formula
Free lean body mass calculator using the Boer formula, with an optional body-fat override for a direct calculation. Metric and imperial.