BMR Calculator
Calculate your Basal Metabolic Rate (BMR) — calories burned at rest.
How to use this tool
- Enter weight, height, age and sex in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your bmr and the full breakdown beneath it.
Calculate your Basal Metabolic Rate (BMR) — calories burned at rest.
⚠ This tool is for general information and education only and is not medical advice. Consult a qualified healthcare professional before making health decisions.
Formula
BMR (male) = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
BMR (female) = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
This is the Mifflin–St Jeor equation.
How it works
This calculator uses the Mifflin–St Jeor equation, published in 1990 and widely regarded as the most accurate BMR formula for general adult populations, to estimate the number of calories your body needs at complete rest to maintain basic physiological functions.
The equation accounts for weight, height, age, and biological sex. It does not factor in individual metabolic variation, body composition, or medical conditions, so actual resting calorie needs may differ by roughly ±10%.
Worked example
- Inputs: 70 kg, 175 cm, age 30, male.
- Apply weight term: 10 × 70 = 700.
- Apply height term: 6.25 × 175 = 1,093.75.
- Apply age term: 5 × 30 = 150.
- Sum with sex constant (male = +5): 700 + 1,093.75 − 150 + 5 = 1,648.75 cal/day.
BMR = 1,648.75 cal/day
Common mistakes to avoid
- Entering weight in pounds and height in feet without converting to kg and cm first, yielding a BMR several times too low.
- Using the Harris-Benedict equation constants in the Mifflin-St Jeor formula (or vice versa) — the constants differ significantly between equations.
- Forgetting that BMR is calories at complete rest; adding activity to BMR manually without a consistent multiplier leads to double-counting.
Key terms
- BMR (Basal Metabolic Rate)
- The minimum number of calories the body burns per day at complete rest to sustain vital functions such as breathing, circulation, and cell production.
- Mifflin–St Jeor equation
- A validated regression formula developed in 1990 that predicts resting energy expenditure from weight, height, age, and sex.
- Calorie (kcal)
- The unit of energy used in nutrition; one kilocalorie is the energy needed to raise 1 kg of water by 1 °C.
- Resting energy expenditure (REE)
- The calories burned at rest; often used interchangeably with BMR, though technically measured under slightly less strict conditions.
- Sex constant
- The fixed offset in the Mifflin–St Jeor equation (+5 for males, −161 for females) that accounts for average physiological differences between sexes.
Frequently asked questions
- What is the difference between BMR and TDEE?
- BMR is calories burned at total rest. TDEE multiplies BMR by an activity factor to estimate actual daily calorie needs.
- Which BMR formula is most accurate?
- Mifflin-St Jeor is generally considered the most accurate for most adults, outperforming the older Harris-Benedict equation in most validation studies.
- Does BMR change with age?
- Yes — BMR decreases roughly 1-2% per decade after age 20 due to loss of lean muscle mass, which is why the formula subtracts 5 x age.