BMR Calculator
Estimate adult resting energy expenditure with the Mifflin–St Jeor equation in metric or US customary units.
Content updated August 7, 2026
The original equation uses sex-specific coefficients. Choose the coefficient applicable to the source data you are using; this is not a statement about gender identity.
This estimates resting energy expenditure, not total daily needs. Illness, pregnancy, body composition, medication and measurement error can materially change actual needs. It is educational, not medical or nutrition advice.
Basal metabolic rate is an estimate of the energy your body uses at rest. This calculator applies the Mifflin–St Jeor resting-energy equation to age, measured height and measured weight, then reports both kilocalories and kilojoules per day.
The original research used separate male and female coefficients and studied healthy adults aged 19–78. The tool keeps that age boundary visible and does not turn BMR into a total daily calorie target.
The BMR formula
Male equation: BMR = 10W + 6.25H − 5A + 5; Female equation: BMR = 10W + 6.25H − 5A − 161W is measured weight in kilograms, H is measured height in centimetres, A is age in completed years, and BMR is estimated kilocalories per day.
Worked example
For a 35-year-old using the male coefficient at 72 kg and 175 cm: 10×72 + 6.25×175 − 5×35 + 5 = 1,643.75, displayed as 1,644 kcal/day.
Assumptions, rounding, and limitations
Assumptions
- The user is an adult aged 19–78, matching the age span in the original derivation sample.
- Weight and height are current measurements and the selected sex-specific equation coefficient is applicable to the source data.
- One kilocalorie is converted to 4.184 kilojoules.
Rounding: The engine retains full floating-point precision; displayed kilocalories and kilojoules are rounded to the nearest whole unit.
Limitations
- This is a population equation, not indirect calorimetry and not a measurement of an individual's metabolism.
- It does not estimate activity, digestion or total daily energy needs and is not medical or nutrition advice.
- Pregnancy, illness, medication and body composition can materially change actual resting expenditure.
Sources
- A new predictive equation for resting energy expenditure in healthy individuals — PubMed / American Journal of Clinical Nutrition
What the Mifflin–St Jeor result represents
The equation estimates resting energy expenditure from four inputs. It does not include walking, work, training, digestion or any activity multiplier, so it should not be read as a complete daily energy requirement.
The source study derived the equation from indirect-calorimetry measurements in 498 healthy adults, including both normal-weight and obese participants. A formula remains an estimate for an individual even when it performs well across a study group.
Use consistent measurements
Use current body weight and standing height without shoes. US customary inputs are converted with one pound equal to exactly 0.45359237 kilogram and one inch equal to exactly 2.54 centimetres before the equation is evaluated.
Illness, pregnancy, unusually high or low lean mass, medications and measurement conditions can all shift actual resting energy expenditure. Indirect calorimetry is the relevant measurement method when a clinical value is needed.
Frequently asked questions
▶What is BMR?
BMR is an estimate of energy used at rest for basic physiological functions. This tool estimates resting energy expenditure and does not include normal daily activity.
▶Which BMR equation does this calculator use?
It uses the simplified Mifflin–St Jeor equations: the male coefficient adds 5 and the female coefficient subtracts 161 after the shared weight, height and age terms.
▶Why is the age input limited to 19–78?
Those are the ages represented in the original derivation study. Restricting the input avoids presenting an extrapolation outside that source population as if it were equally supported.
▶Is BMR the same as daily calorie needs?
No. BMR covers estimated resting energy only. Total daily expenditure also includes activity and digestion, and cannot be determined from this result alone.
▶How are pounds and inches converted?
Pounds are multiplied by 0.45359237 for kilograms and inches by 2.54 for centimetres before applying the metric equation.
Related calculators
Find how many calories you need each day to maintain, lose, or gain weight, based on your body and activity.
Open calculator →Compare estimated daily maintenance energy with planned average intake across a chosen number of weeks.
Open calculator →Calculate your Body Mass Index from height and weight, in metric or imperial units, with your category.
Open calculator →Disclaimer: BMR Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.