BMR Calculator
How many calories does your body burn doing nothing?
About BMR Calculator
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to sustain essential life functions — breathing, circulation, temperature regulation, and cell production. It represents the minimum caloric floor below which intake should never fall. The Mifflin-St Jeor equation, validated by the American Journal of Clinical Nutrition in 1990, is the most accurate BMR formula for the general population and is the preferred standard used by dietitians and clinicians worldwide.
Male: 10×W + 6.25×H − 5×A + 5 Female: 10×W + 6.25×H − 5×A − 161 (Mifflin-St Jeor Equation, 1990)
Source: Mifflin MD et al., 1990 — American Journal of Clinical Nutrition · Harris-Benedict Equation (Revised, 1984) · WHO Technical Report on Nutrition and Energy Requirements
Which Activity Level Are You?
Most people either underestimate or overestimate their activity level — and the wrong multiplier can throw your daily calorie target off by 200–400 calories. Use these real-world descriptions to identify where you genuinely fall:
Sedentary
Little or no planned exercise. Your day is mostly sitting — desk work, driving, light walking between rooms. You don't have a gym routine.
Lightly Active
Light exercise 1–3 days a week, or a job that keeps you on your feet for part of the day. Think: casual walks, light yoga, or a retail/teaching role.
Moderately Active
Moderate exercise 3–5 days a week with a desk job otherwise. The typical gym-goer — 45–60 min sessions, 4 days a week, seated work the rest of the time.
Very Active
Hard exercise or sports 6–7 days a week, or a physically demanding job. You train most days with real intensity — this is less common than people assume.
Extra Active
Professional-level training, twice-daily sessions, or an extremely demanding physical job combined with structured exercise. Applies to very few people.
Why Your BMR Result Matters
Your BMR is not just a number — it is a window into your metabolic health. Research consistently links poor BMR awareness to under-eating, over-eating, and long-term metabolic dysfunction. Understanding your BMR gives you the evidence base to make informed decisions about nutrition, activity, and wellbeing.
Weight Management Foundation
Eating below your BMR triggers the body to break down muscle for energy and slow its metabolic rate — the opposite of healthy weight loss. Your BMR is the caloric floor that keeps any deficit sustainable.
Muscle Mass Preservation
Muscle is metabolically active tissue that raises your BMR. Adequate intake at or above BMR — paired with resistance training — protects lean mass during weight loss and supports a stronger metabolism long-term.
Metabolic Decline with Age
BMR drops approximately 1–2% per decade after age 20 as muscle mass naturally declines. Knowing your current BMR lets you adapt nutrition early and use strength training to slow — and partially reverse — that decline.
How to Use BMR Most Effectively
BMR is a powerful foundation, not an absolute figure. It is an estimate based on population-level equations — your true BMR may vary. Understanding how to apply it correctly ensures your calorie planning is both accurate and sustainable:
Multiply by your activity level to find real calorie needs
BMR alone reflects rest. Your actual daily calorie need (TDEE) is BMR multiplied by your activity level: 1.2 for sedentary up to 1.9 for extra active. Always use TDEE — not BMR — as the basis for any weight loss or gain target.
Account for muscle mass — it changes the result
Muscle burns more calories at rest than fat. Two people of the same weight, height, and age can have meaningfully different BMRs due to body composition. If you train regularly, pair your BMR with a body fat reading for greater accuracy.
BMR is a starting point, not a fixed truth
The formula is an estimate based on population averages. Hormonal conditions, medications, and body composition changes can shift your actual BMR. Recalculate every few months or after significant changes to your body or lifestyle.