BMR Calculator
Calculate your basal metabolic rate with the Mifflin-St Jeor equation and see your calorie needs at every activity level.
BMR Calculator — input your values
What does this health calculator do?
This BMR calculator estimates your basal metabolic rate — the calories your body burns at complete rest just to keep your heart beating, lungs breathing and cells working. It uses the Mifflin-St Jeor equation, one of the most accurate validated formulas for this purpose.
The result is shown as a daily number plus per-hour and per-week equivalents, and then scaled across five activity levels so you can see how your total calorie needs change from sedentary to extra active.
BMR is a useful baseline, but your true daily burn depends on movement, muscle mass and hormones. Use this as an estimate and talk to a healthcare professional before making significant dietary changes.
Formula and variables
To get total daily energy expenditure (TDEE), multiply BMR by an activity factor between 1.2 and 1.9.
| Symbol | Meaning |
|---|---|
| w | Weight in kilograms |
| h | Height in centimeters |
| a | Age in years |
Worked example
A 30-year-old woman, 165 cm, 60 kg.
- BMR = 10 × 60 + 6.25 × 165 − 5 × 30 − 161.
- BMR = 600 + 1,031.25 − 150 − 161 = 1,320.25 kcal/day.
- With moderate activity (× 1.55): 1,320.25 × 1.55 ≈ 2,046 kcal/day.
Answer: BMR ≈ 1,320 kcal/day.
Tips and common mistakes
Tips
- BMR is slightly higher for people with more muscle mass, so resistance training can nudge it upward.
- A low-carb or very low-calorie diet can temporarily lower BMR — gradual changes are gentler on metabolism.
- BMR reflects rest only; add activity calories on top to plan daily intake.
- Retest every few kilograms of weight change, since BMR tracks body size.
Common mistakes to avoid
- Confusing BMR with TDEE — one is resting burn, the other includes activity.
- Using pounds or inches directly in the equation without converting to kilograms and centimeters.
- Expecting a precise number; equations are accurate within roughly 10% for most people.
BMR Calculator — frequently asked questions
What is BMR?
Basal metabolic rate is the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation and temperature regulation.
What is the Mifflin-St Jeor equation?
It estimates BMR as 10 × weight in kg + 6.25 × height in cm − 5 × age, adding 5 for men or subtracting 161 for women.
What's the difference between BMR and TDEE?
TDEE (total daily energy expenditure) includes everything you burn through movement, exercise and digestion. Multiply your BMR by an activity factor of 1.2 to 1.9 to estimate it.
Can I increase my BMR?
To a degree — building muscle raises resting burn, as does staying active. Aging and weight loss tend to lower it, which is why needs change over time.
Why do two people of the same size have different BMRs?
Muscle mass, genetics, hormones and even body temperature all influence metabolic rate, so equations can only give an average estimate.
Is BMR measured differently in a lab?
Yes — clinical measurement uses indirect calorimetry, which analyzes oxygen use and carbon dioxide output, often after an overnight fast. Home formulas approximate the same concept.