BMR Calculator 2025 – Basal Metabolic Rate Explained

Introduction

Your BMR (Basal Metabolic Rate) is the number of calories your body burns just to stay alive—breathing, circulating blood, and growing cells. It accounts for ~60-70% of your total daily energy expenditure.

Knowing your BMR is the first step to losing or gaining weight.

BMR Formulas (Mifflin-St Jeor)

This is considered the most accurate modern formula.

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5

Women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

Calculation Example

30-year-old Man, 180cm (5'11"), 80kg (176 lbs):

• Weight: 10 × 80 = 800
• Height: 6.25 × 180 = 1,125
• Age: 5 × 30 = 150
• Math: 800 + 1,125 - 150 + 5 = 1,780 calories/day

This means he burns 1,780 calories doing nothing.

From BMR to TDEE (Total Daily Energy Expenditure)

To find your maintenance calories, multiply BMR by your activity level:

• Sedentary (desk job): BMR × 1.2
• Lightly Active (1-3 days exercise): BMR × 1.375
• Moderately Active (3-5 days): BMR × 1.55
• Very Active (6-7 days): BMR × 1.725
• Athena/Athlete: BMR × 1.9

Example (Sedentary from above):

• 1,780 × 1.2 = 2,136 calories to maintain weight

BMR vs. BMI

• BMI (Body Mass Index): Ratio of weight to height. Measures "size".
• BMR (Basal Metabolic Rate): Energy output. Measures "fuel needs".

A bodybuilder has a high BMI (overweight) and high BMR (needs lots of food).

FAQ

Q: Can I increase my BMR? A: Yes. Muscle burns more calories than fat. Lifting weights and building muscle increases your resting metabolic rate.

Q: Does eating less lower BMR? A: Yes. Crash dieting causes "metabolic adaptation" where your body slows down to conserve energy. This is why slow weight loss is better.

Q: Is BMR the same as RMR? A: Roughly. RMR (Resting Metabolic Rate) includes minor movements and eating digestion. BMR is strictly "coma" state. They are usually within 10% of each other.

Conclusion

Don't guess your calories. Calculate your BMR, apply your activity factor, and subtract 500 for sustainable weight loss (1 lb/week).