Find out how many calories your body burns at rest. This free BMR calculator uses the Mifflin-St Jeor equation and adds your activity level to estimate your daily maintenance calories (TDEE).
BMR is the energy your body uses at rest; TDEE adds your activity. These are estimates – for personal nutrition guidance, talk to a doctor or registered dietitian.
How BMR Calculator Works
This tool estimates your Basal Metabolic Rate — the calories your body burns at rest just to keep your organs and systems running — then multiplies it by your activity level to estimate total daily calorie needs (TDEE). It uses the Mifflin-St Jeor equation, a widely used formula in nutrition science.
Formula: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5 for men, or − 161 for women. TDEE = BMR × activity factor, where the factor ranges from 1.2 (sedentary) to 1.9 (very active). Imperial inputs are converted to kg and cm before the formula runs.
- Sex — male or female, since the equation’s constant term differs by sex
- Age — your age in years
- Height — your height in centimeters, or feet and inches in imperial mode
- Weight — your body weight in kilograms, or pounds in imperial mode
- Activity level — sedentary, light, moderate, active, or very active, used to scale BMR up to TDEE
Example Scenarios
| Sex | Age | Height (cm) | Weight (kg) | Activity | BMR / TDEE |
|---|---|---|---|---|---|
| Male | 30 | 175 | 70 | Moderate (1.55) | 1649 / 2556 cal/day |
| Female | 25 | 160 | 55 | Sedentary (1.2) | 1264 / 1517 cal/day |
| Male | 45 | 180 | 85 | Active (1.725) | 1755 / 3027 cal/day |
| Female | 35 | 165 | 65 | Light (1.375) | 1345 / 1850 cal/day |
| Male | 50 | 170 | 78 | Very active (1.9) | 1598 / 3035 cal/day |
| Female | 60 | 155 | 60 | Moderate (1.55) | 1108 / 1717 cal/day |
BMR Calculator FAQ
What’s the difference between BMR and TDEE?
BMR is the calories your body burns at complete rest, just to stay alive. TDEE takes that number and multiplies it by an activity factor to estimate the total calories you burn in a full day, including movement and exercise.Why does the Mifflin-St Jeor equation use different constants for men and women?
The equation adds 5 for men and subtracts 161 for women, reflecting average differences in body composition, such as muscle mass, between sexes at similar height, weight, and age in the population data it was built from.How accurate is BMR estimated from a formula versus measured directly?
Formula-based BMR is an estimate, not a lab measurement. Mifflin-St Jeor is considered one of the more accurate predictive equations for the general population, but individual metabolism can still vary from what any formula predicts.Should I eat exactly at my BMR to lose weight?
No — BMR alone doesn’t account for daily activity. Eating at or below BMR for extended periods isn’t a general recommendation; most people reference TDEE, which includes activity, when thinking about calorie targets for weight goals.How does activity level change my calorie needs?
The activity factor scales your BMR up: sedentary uses 1.2, light exercise 1.375, moderate 1.55, active 1.725, and very active 1.9. Choosing a level that’s too high relative to your actual activity will overestimate your calorie needs.Why do age and height affect BMR the way they do?
The formula adds calories for greater height and subtracts them for greater age, reflecting that metabolism tends to decline gradually over the years while a larger body frame generally requires more energy to maintain at rest.Related Calculators
Once you know your TDEE, the TDEE calculator can help you fine-tune it for cutting or bulking goals, and the calorie calculator can translate that number into a daily calorie target. For a full nutrition breakdown, the macro calculator splits your calories into protein, carbs, and fat.