What Is BMR and How to Calculate It
Your BMR is the calories your body burns at rest. Learn how to calculate it, what affects it, and how it guides your diet.
BMR — your Basal Metabolic Rate — is the number of calories your body burns just to stay alive at complete rest. Knowing it is the foundation of any sensible plan to lose, gain or maintain weight, because it tells you the minimum energy your body needs each day.
What BMR really measures
Even while you sleep, your body spends energy on breathing, circulating blood, and repairing cells. BMR captures exactly that baseline. Add your daily activity on top and you get your total calorie needs, known as TDEE (Total Daily Energy Expenditure).
The formula most experts use
The trusted Mifflin-St Jeor equation estimates BMR from four inputs: your weight, height, age and sex. It is more accurate than older formulas, which is why most calculators and dietitians rely on it today.
What affects your BMR
- Muscle mass — more muscle burns more calories at rest.
- Age — BMR gradually falls as you get older.
- Sex — men usually have a higher BMR than women.
- Body size — larger bodies need more energy.
BMR vs TDEE
| Term | What it is |
|---|---|
| BMR | Calories burned fully at rest. |
| TDEE | BMR plus your daily activity. |
Remember it is an estimate
BMR formulas give a close estimate, not a lab-precise number. Use it as a starting point and adjust based on real results over a few weeks.
Calculate yours instantly
You do not need to do the arithmetic yourself. Our BMR and calorie calculator gives both your BMR and daily calorie needs in one click, and to check whether your weight sits in a healthy range the BMI calculator is a useful companion. For trustworthy, science-based guidance, the U.S. National Institute of Diabetes and Digestive and Kidney Diseases publishes free resources at NIDDK.nih.gov. Know your baseline, then plan your meals around it.