BMR Calculator
Estimated BMR
Estimated resting energy expenditure using the Mifflin-St Jeor equation.
What Is BMR?
Basal metabolic rate describes the minimum energy your body needs to maintain essential functions while at rest, such as breathing, circulation and basic cellular activity.
Most online BMR calculators do not directly measure this energy use. They estimate it from variables such as age, height, weight and sex.
Need.fit uses the Mifflin-St Jeor equation. The original research described the output as resting energy expenditure, so the number on this page should be treated as a resting-energy estimate rather than an exact laboratory BMR.
How It's Calculated
The calculator uses your weight, height, age and the sex constant in the Mifflin-St Jeor equation. For men, the formula is REE = 10W + 6.25H - 5A + 5. For women, the formula is REE = 10W + 6.25H - 5A - 161. The result estimates resting energy expenditure in kilocalories per day. A prediction equation cannot measure individual metabolism directly. Among the commonly used equations reviewed by Frankenfield and colleagues, Mifflin-St Jeor was more likely than the others to estimate measured RMR within 10%, but individual prediction errors and population limitations still exist.
REE = 10W + 6.25H - 5A + s
- W = body weight in kilograms
- H = height in centimeters
- A = age in years
- s = +5 for men and -161 for women
What to Do With Your Result
Treat your estimated BMR as a resting-energy baseline, not as your recommended daily calorie intake. Eating exactly your BMR is not what this calculator is designed to prescribe.
BMR or a resting-energy estimate reflects energy used at rest. TDEE estimates total daily energy expenditure after accounting for daily movement and training, so use the TDEE Calculator when you want an estimate of total daily calorie use.
For a broader maintenance-calorie estimate, use the Calorie Calculator. Need.fit can then use your goal, schedule and progress to build a more useful plan around those estimates.