What is BMR?
Basal metabolic rate is the amount of energy your body uses to maintain essential functions at rest, including breathing, circulation, temperature regulation, and organ function. A true laboratory BMR is measured under strict basal conditions. Online BMR calculators usually estimate resting energy from prediction equations instead of measuring metabolism directly.
This calculator uses the familiar term BMR while clearly separating the estimate from a clinical measurement. See the methodology for the measurement and terminology details.
How is BMR calculated?
The primary estimate uses the Mifflin–St Jeor equation, which predicts resting energy expenditure from body weight, height, age, and the sex coefficient used in the published equation.
Example BMR calculation
For a 30-year-old male who weighs 70 kg and is 175 cm tall:
10 × 70 + 6.25 × 175 − 5 × 30 + 5 = 1,648.75
The displayed estimate is 1,649 kcal/day.
BMR vs RMR vs TDEE
BMR refers to energy use under strict basal conditions. RMR or resting energy expenditure is measured under less restrictive resting conditions. TDEE includes resting energy plus physical activity and the thermic effect of food.
A BMR estimate is therefore not the same as a daily calorie target. This calculator deliberately keeps TDEE and diet targets separate.
How accurate is a BMR calculator?
Prediction equations estimate population averages and cannot measure an individual metabolism directly. Mifflin–St Jeor is widely used for adults and has performed well in systematic comparisons of common equations, but individual error can still be meaningful.
Accuracy may be lower when a person differs substantially from the populations used to develop or validate the equations. Body composition, age, severe obesity, major weight change, athletic training, illness, pregnancy, and measurement conditions can all affect interpretation. Read the research references and accuracy FAQ for the evidence behind these notes.
What affects basal metabolic rate?
Resting energy use is strongly related to body size and fat-free mass. Age, sex-related physiological differences, body composition, and some health or life-stage factors can also influence measured resting expenditure. Prediction equations use only a small set of variables, which is why two people with similar calculator inputs can still have different measured values.
Common BMR calculator questions
Which BMR formula does this calculator use?
Mifflin–St Jeor is the primary adult estimate. Revised Harris–Benedict is displayed separately for comparison. Cunningham and Ten Haaf appear only when the relevant optional context is supplied.
Can I use pounds and feet?
Yes. Choose Imperial and enter feet, inches, and pounds. The values are converted before the equation is calculated.
Is BMR the number of calories I should eat?
No. BMR estimates resting energy only. Daily energy needs also depend on activity and other components of total energy expenditure.
Why does the calculator show more than one equation?
Different prediction equations were developed from different datasets. Showing them separately gives useful context without pretending that averaging them creates a more accurate personal result.
Is this calculator for children?
No. This version is for adults age 18 and older. Pediatric energy estimation requires age-specific methods and growth considerations.
Sources and calculation policy
The calculator documents its equations, units, source studies, and interpretation limits. No formula is presented as a direct measurement of metabolism.
Read the methodology · View the research references · About this calculator