What is BMR?
Basal Metabolic Rate (BMR) estimates the calories your body burns at rest to sustain vital functions like breathing, circulation, and cell production—typically 60-70% of daily energy use. It's key for weight management: Knowing BMR helps set calorie targets (e.g., subtract 500 for loss). In 2025, with obesity affecting 42% of U.S. adults (CDC), BMR tools guide sustainable nutrition, though BMR differs slightly from Resting Metabolic Rate (RMR), measured more casually.
This calculator uses the Mifflin-St Jeor equation—more accurate for modern populations than Harris-Benedict—for precise estimates. Factors: age, gender, height, weight. Not diagnostic; varies by muscle mass, hormones, or conditions.
How to Use BMR Calculator
Input age, gender, height (inches), weight (lbs). Computes BMR via Mifflin-St Jeor:
- Men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5
- Women: ... -161 instead of +5
(Converts units internally.) Outputs BMR; multiply by activity factor for TDEE (e.g., 1.2 sedentary). Harris-Benedict alternative available via dropdown.
Sample: 30-year-old woman, 5'4" (64 in), 150 lbs. BMR: 1,346 calories. TDEE (lightly active): ~1,851.
Activity Multipliers for TDEE
- Sedentary (desk job): ×1.2
- Lightly Active (1-3 days exercise): ×1.375
- Moderately Active (3-5 days): ×1.55
- Very Active (6-7 days): ×1.725
- Super Active (intense + job): ×1.9
Tips for Using BMR
Weight Loss: Create 500-cal deficit below TDEE for ~1 lb/week loss; prioritize protein (0.8-1g/lb body weight) to preserve muscle. Track progress bi-weekly. Bodybuilding/Gain: 250-500 cal surplus; focus carbs for energy, train 4-6x/week. Avoid excess protein (>0.9g/lb doesn't boost gains). General: Recalculate every 10-20 lbs change; combine with apps for macros. Hydrate, sleep 7-9 hours—boosts metabolism 5-20%.
Frequently Asked Questions
BMR vs. RMR?
- BMR: Strict lab conditions (fasted, rested). RMR: Everyday rest estimate—often used interchangeably, ~10% higher.
How accurate at home?
- ±10-20% variance; lab tests (indirect calorimetry) gold standard, but formulas suffice for planning.
Does it factor activity?
- No—BMR is resting only. Use multipliers for full TDEE.
Safe calorie cuts?
- Women: ≥1,200/day; Men: ≥1,500. Gradual (200-300 cal) prevents fatigue, nutrient gaps.
Disclaimers
Estimates only—not medical advice. Inaccurate for pregnant, elderly, or ill; consult doctor/dietitian. Mifflin-St Jeor best for adults 18-65. CDC/WHO data (2025). No liability for health outcomes.
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