BMR Calculator
Resting calorie burn from age, sex, height, and weight using the Mifflin St Jeor equation.
What it does
Basal metabolic rate is the energy your body uses at complete rest to keep breathing, circulating blood, and maintaining organs. It is the largest single part of daily calorie burn, before any movement or digestion is added.
The tool above uses the Mifflin St Jeor equation, the standard reference for estimating BMR from age, sex, height, and weight. Pick metric or imperial, enter your numbers, and read the resting burn per day.
BMR is not the same as the calories you need to maintain weight. That number, called TDEE, layers daily movement, exercise, and digestion on top of BMR. This page shows rest only.
Men typically hold a higher BMR than women at the same size because of greater lean mass. BMR also drifts lower with age as muscle mass tends to fall.
How to use
- Pick metric (kg, cm) or imperial (lb, in) first.
- Enter your age in years.
- Pick male or female.
- Enter weight and height in the active units.
- Read BMR first, then the daily low and high range.
Formula
- weight_kg
- Body weight in kilograms.
- height_cm
- Body height in centimeters.
- age
- Age in years.
- 5 / -161
- Sex constant: plus 5 for male, minus 161 for female.
Mifflin St Jeor is the most widely cited BMR equation. It estimates rest only and does not count activity, illness, or muscle mass differences, so treat the result as a starting point.
Worked example
Example: 30 year old man, 70 kg, 175 cm
Age 30, male, weight 70 kg, height 175 cm, metric units.
- Weight term: 10 x 70 = 700.
- Height term: 6.25 x 175 = 1,093.75.
- Age term: 5 x 30 = 150.
- Add male constant: 700 + 1,093.75 - 150 + 5 = 1,648.75.
- Round: 1,649 kcal per day at rest. Range 1,484 to 1,814 kcal.
Reference table
| Weight | Height | BMR per day |
|---|---|---|
| 60 kg | 170 cm | 1,518 kcal |
| 70 kg | 175 cm | 1,649 kcal |
| 80 kg | 180 cm | 1,780 kcal |
| 90 kg | 185 cm | 1,911 kcal |
Limits
- BMR estimates rest only and ignores activity, illness, and digestion.
- The equation is less accurate at very high or very low body fat.
- Muscle mass and genetics shift real burn away from the estimate.
- Use this as a starting point, not a prescription.
Common mistakes
- Confusing BMR with daily maintenance calories, which are higher.
- Using imperial numbers in metric fields without converting.
- Forgetting that BMR falls with age and muscle loss.
- Treating the single number as exact rather than an estimate.
- Using athlete or pregnant body composition without adjustment.
Try it yourself
Quick checks. Answers sit tucked under each question.
25 year old woman, 60 kg, 165 cm?
BMR about 1,345 kcal per day (10x60 + 6.25x165 - 5x25 - 161).
40 year old man, 80 kg, 180 cm?
BMR about 1,730 kcal per day.
30 year old man, 154 lb, 69 in?
BMR about 1,649 kcal per day, same as metric mirror.
Questions
What does BMR mean?
Basal metabolic rate: calories burned at complete rest to keep vital organs running.
Is BMR the same as maintenance calories?
No. Maintenance adds movement, exercise, and digestion on top of BMR.
Why do men and women differ?
Men typically carry more lean mass, which burns more calories at rest.
Does BMR change with age?
Yes. It generally drifts lower as muscle mass falls and metabolism slows.
Which equation is used?
Mifflin St Jeor, the standard reference for BMR estimation.
Can I lose weight by eating at BMR?
Eating at BMR creates a deficit for most people, but it is not a diet plan. Talk to a clinician first.