Free BMR Calculator
Basal Metabolic Rate (BMR) is the energy your body uses at rest for essential functions. This calculator uses the Mifflin–St Jeor equation as a practical estimate; individual measured resting energy can differ.
Last updated: July 2026 · Formula: (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5 (male) or − 161 (female). For adults 18+.
Calculate your BMR
Enter your measurements below to discover your daily caloric baseline:
Understanding BMR
Your Basal Metabolic Rate represents the energy your body needs while at complete rest. Think of it as the calories required to power essential functions like breathing, circulation, and cell production - even when you're sleeping.
This baseline doesn't account for any physical activity, from walking to intense exercise, which would increase your total daily calorie needs.
Scientific Approach
kkal.ai uses the Mifflin–St Jeor equation because it is widely studied and needs only age, sex, height, and weight. Cross-validation research also shows that every predictive equation can have meaningful individual error.
Frequently Asked Questions
What is BMR?
BMR (Basal Metabolic Rate) describes energy used at complete rest for essential functions such as breathing, circulation, and cell maintenance. This equation estimates that baseline; it does not measure your full daily expenditure.
What's the difference between BMR and TDEE?
BMR is calories burned at rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor (1.2 sedentary up to 1.9 extra active), which adds in calories burned through movement, exercise, and digestion. TDEE is the number you actually eat against for weight loss or gain.
How accurate is a BMR formula?
No prediction equation is exact for every person. Mifflin–St Jeor is a reasonable starting point for many adults, but body composition, population, health status, and weight change can affect error. Indirect calorimetry is a measurement; this calculator is not.
Why is my BMR different from someone with the same weight?
People at the same weight can have different resting energy needs because age, sex, body composition, health, and other factors differ. Mifflin–St Jeor adjusts for age and sex but does not measure body composition directly.
Is the kkal.ai BMR calculator free?
Yes. The BMR calculator, macro calculator, and AI meal photo tracker are free to use on the web with no account required.
Sources and limitations
- Original Mifflin–St Jeor equation paper
- Cross-validation of resting metabolic-rate equations
- Body-composition-based validation study
Do not use this estimate as individualized treatment. Needs can differ during pregnancy, growth, illness, medication use, or eating-disorder recovery.