What this estimate does not cover
- Pick your unit system. Everything below switches with it.
- Select your sex — the equation uses a different constant for each.
- Enter your age, weight and height. The result updates as you type.
- Copy the link if you want to keep or share this exact result.
The ranges shown next to each field are the ranges the original study used, not arbitrary limits. Outside them the equation has not been shown to hold.
Mifflin and St Jeor published this in 1990 after measuring 498 healthy adults once at baseline. It replaced the older Harris-Benedict equation and is the standard resting-energy estimate in clinical nutrition.
BMR counts energy used at rest only. You burn far more than that across a normal day — walking, working, thinking, digesting food. The usual total is obtained by multiplying BMR by an activity factor.
We deliberately do not publish a TDEE figure here. The widely circulated activity multipliers (1.2, 1.375, 1.55, 1.725, 1.9) are not established by the Mifflin-St Jeor paper, and presenting them as if they were would be stating something the source does not support.
How accurate is this?
It is an estimate produced by a regression, not a measurement. Fat-free mass predicts resting energy expenditure better than anything you can enter in a form, so treat the result as a well-founded starting point rather than a precise reading of your body.
Why is there an age limit of 19 to 78?
That is the range of the 498 adults measured in the 1990 study. The equation was never validated below 19 or above 78, so we do not extrapolate past it — especially not for children, where the equation is known to perform poorly.
Should I use this while pregnant or breastfeeding?
No. Pregnancy and lactation were not part of the study, and energy needs change substantially in both. Speak to a doctor or registered dietitian instead.
Why does it ask for my sex?
The equation has a sex-specific constant: +5 for men and −161 for women. It is the measured difference in the study, not an assumption about ability or fitness. The underlying biology is more nuanced than the two-category split this 1990 paper used.
Does my result change if I enter it in pounds and inches?
No. Imperial inputs are converted to metric first and then run through the identical equation, so both routes give the same number for the same person.
Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. The American Journal of Clinical Nutrition. 1990;51(2):241–247. doi:10.1093/ajcn/51.2.241
Population studied: 498 healthy adults aged 19–78 years, measured once at baseline. This calculator reproduces the sex-specific form exactly as published.