BMR Calculator
Calculate Basal Metabolic Rate in kcal/day from age, sex, weight, height.
Written by Golam Rabbani, Founder & Lead Engineer — Last updated 2026-05-01
How to use this bmr calculator
- Enter your age and select your gender.
- Toggle kg/lbs, then enter your body weight.
- Toggle cm/ft, then enter your height.
- Choose a formula — Mifflin-St Jeor is recommended for most adults; pick Katch-McArdle if you know your body-fat %.
- Press Calculate to see your Basal Metabolic Rate in kcal/day.
About this bmr calculator
The BMR calculator estimates how many calories your body burns at complete rest over 24 hours to keep core functions like breathing, circulation, and cell repair running. It supports three established equations: Mifflin-St Jeor (the default; widely cited as the most accurate predictor for the general adult population), the revised Harris-Benedict equation, and Katch-McArdle (which uses lean body mass via body-fat %).
The default Mifflin-St Jeor formula is: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 for males, or − 161 for females, as published by Mifflin MD, St Jeor ST, et al. (Am J Clin Nutr. 1990;51(2):241-7). Katch-McArdle uses BMR = 370 + (21.6 × lean body mass in kg). This is an estimate for informational purposes and is not a substitute for advice from a qualified clinician.
For example, a 30-year-old male who weighs 80 kg and is 180 cm tall, using Mifflin-St Jeor, has a BMR of 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1125 − 150 + 5 = 1,780 kcal/day. The tool is useful for setting maintenance calories, planning a deficit or surplus, and comparing how the three formulas differ on the same inputs.
FAQ
- What is BMR?
- Basal Metabolic Rate is the energy your body uses at complete rest in a thermoneutral environment to keep vital organs working. It typically accounts for 60–75% of your total daily energy expenditure.
- Which formula should I pick?
- Mifflin-St Jeor is the standard recommendation for most adults. Use Harris-Benedict if you want to compare with older sources. Use Katch-McArdle only if you have a reliable body-fat % measurement — it tends to be more accurate for lean or muscular people because it works from lean body mass.
- How is BMR different from TDEE?
- BMR is your at-rest energy burn. TDEE multiplies BMR by an activity factor (1.2–1.9) to account for movement, exercise, and the thermic effect of food.
- Why do men and women get different BMRs at the same weight?
- Men typically have a higher lean-mass percentage, which burns more calories than fat tissue. The Mifflin-St Jeor formula adjusts for this with a +5 constant for males and −161 for females.
- Does this tool store my data?
- No. All calculations run in your browser. Your age, weight, height, and body-fat % are never sent to a server and are cleared when you close the tab.
- Is the BMR calculator free?
- Yes — fully free, no signup, no account, no usage limits.