BMR Calculator
Mifflin-St Jeor basal metabolic rate. See calories burned at complete rest, then estimate TDEE from your activity level.
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These terms are often confused. This calculator gives you BMR (calories at complete rest). Multiply by an activity factor for TDEE (total daily burn). RMR is a similar lab measurement, usually slightly higher than BMR.
| Term | What it measures | Use for |
|---|---|---|
| BMR | Calories at complete rest | Baseline metabolism, formula comparison |
| TDEE | BMR + all daily activity | Cut, bulk, or maintenance calories |
| RMR | Calories at relaxed rest (~5-10% above BMR) | Clinical tests; similar to BMR in practice |
After your BMR result, pick an activity level above to estimate TDEE. For full cut/bulk targets, use the Calorie Calculator or TDEE Calculator.
Activity Factors: 1.2 to 1.9 (and Where They Come From)
To turn BMR into TDEE you multiply by an activity factor. The standard multipliers 1.2, 1.375, 1.55, 1.725, and 1.9 originate from the physical activity level (PAL) categories in the Harris-Benedict methodology as revised by Roza and Shizgal (1984) and are the same factors referenced by the Academy of Nutrition and Dietetics for estimating energy needs.
| Factor | Activity level | Typical week |
|---|---|---|
| 1.2 | Sedentary | Desk job, little or no exercise |
| 1.375 | Lightly active | Light exercise 1-3 days/week |
| 1.55 | Moderately active | Moderate exercise 3-5 days/week |
| 1.725 | Very active | Hard exercise 6-7 days/week |
| 1.9 | Extra active | Hard daily exercise plus a physical job |
Most lifters who train 3-5 times per week and sit the rest of the day land at 1.375-1.55, not higher. Overshooting the factor is the most common reason calculated TDEE feels too high.
How to Use BMR for Cutting or Bulking
BMR itself is not an eating target. Turn it into calories in three steps:
- Calculate BMR with the calculator above (Mifflin-St Jeor).
- Multiply by your activity factor from the table to get TDEE (maintenance calories).
- Adjust for your goal: cutting is TDEE minus 300-500 kcal/day (about 0.25-0.5 kg/week of loss). Bulking is TDEE plus 200-300 kcal/day to gain muscle while limiting fat gain. Never eat below your BMR for extended periods.
The Calorie Calculator does steps 2-3 for you, and the Macro Calculator splits the result into protein, carbs, and fat.
What Is Basal Metabolic Rate (BMR)?
Your Basal Metabolic Rate (BMR) is the number of calories your body burns every day at complete rest. It powers breathing, blood circulation, brain function, cell repair, and temperature regulation. BMR typically accounts for 60-70% of your total daily calorie expenditure.
For lifters, BMR matters because muscle mass raises resting burn. Strength training is the most reliable way to increase BMR over time without extreme dieting.
The Formulas Behind This Calculator
- Mifflin-St Jeor (recommended) — The most accurate equation for the general population according to the American Dietetic Association. Uses weight, height, age, and sex.
- Harris-Benedict — One of the oldest BMR equations (1919, revised 1984). Tends to overestimate by 5-15% compared to modern measurements but is still widely referenced.
Factors That Affect Your BMR
- Muscle mass — More muscle means a higher BMR. Strength training is the most effective way to increase resting metabolism.
- Age — BMR decreases roughly 1-2% per decade after age 20, mainly due to muscle loss.
- Sex — Males typically have a higher BMR due to greater lean mass and higher testosterone.
- Body size — Larger bodies burn more calories at rest because there is more tissue to maintain.
- Dieting history — Prolonged calorie restriction can reduce BMR through metabolic adaptation.
Frequently Asked Questions
Related Free Tools
- Calorie Calculator — TDEE plus cutting, maintenance, and bulking calorie targets.
- TDEE Calculator — Full daily burn breakdown: BMR, NEAT, TEF, and exercise.
- Macro Calculator — Daily protein, fat, and carb targets from your calorie goal.
- Body Fat Calculator — Estimate body fat with the Navy method for lean-mass-based formulas.
Last updated July 2, 2026 · Reviewed by Dawid Kowalczyk, Personal Trainer & IFBB Competitor