Nutrition1 min read·Updated March 9, 2026
Basal Metabolic Rate (BMR): What It Is and How to Calculate It
Understand your basal metabolic rate, how it's calculated using the Mifflin-St Jeor equation, and how to use BMR for weight management.
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What Is Basal Metabolic Rate?
BMR is the number of calories your body needs to sustain basic life functions at complete rest — breathing, circulation, cellular repair. It represents calories burned if you lay in bed all day. BMR accounts for roughly 60–75% of total daily calorie expenditure.
Mifflin-St Jeor Equation (most accurate)
- Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
- Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
BMR vs. TDEE
BMR is calories at rest. TDEE = BMR × activity multiplier. Sedentary: TDEE ≈ 1.2× BMR. Highly active: TDEE ≈ 1.7–1.9× BMR. Your calorie goal for weight management is based on TDEE, not BMR.
What Affects BMR
- Muscle mass: Muscle is metabolically active — 10 lbs of muscle raises BMR by ~60–100 calories/day
- Age: BMR decreases roughly 1–2% per decade after age 20
- Calorie restriction: Significant restriction lowers BMR (adaptive thermogenesis)
- Thyroid function: Hypothyroidism can reduce BMR by 10–20%
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Frequently Asked Questions
Is BMR the same as resting metabolic rate (RMR)?
They're close but not identical. Most online calculators actually calculate RMR (measured under less strict conditions, typically 10–20% higher than true BMR) but call it BMR.
Can I increase my BMR?
Yes. Building muscle mass is the most significant way. Resistance training 3–4x/week over months adds meaningful muscle mass. Adequate sleep and avoiding prolonged severe calorie restriction also prevent BMR from declining.