BMR Calculator — Basal Metabolic Rate

Estimate the calories your body burns at complete rest, using three published equations.

  • Nutrition
  • 2 cited sources
  • Runs in your browser
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Unit system

Your estimated basal metabolic rate

1,749 kcal/day

This estimates the energy your body uses at complete rest. Your full daily burn is higher — see the TDEE calculator to include activity. Estimates commonly sit within about 10% of measured values.

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

  1. 01 Mifflin MD, St Jeor ST, et al. Am J Clin Nutr 1990;51:241–247
  2. 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 — breathing, circulation, cell maintenance. It typically makes up 60–75% 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.

Written and reviewed by Mathew Beale — MSc Biotechnology, University of Reading.

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