The Starting Point for Any Diet or Fitness Plan
Whether you're cutting calories to lose weight, eating at maintenance, or bulking to gain muscle — everything starts with knowing your BMR. Without it, calorie targets are just guesses.
BMR Calculator
Calculate your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation. Find the minimum calories your body burns at rest. Includes BMR formula breakdown.
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How to use BMR Calculator
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Enter your sex, age, height, and current weight (supports both metric and imperial units).
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The calculator uses the Mifflin-St Jeor equation — the most accurate formula for estimating resting calorie needs in modern adults.
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Your BMR result is your daily calorie floor. Multiply it by your activity level to get your TDEE and set your diet targets.
Why use this tool?
Uses the Mifflin-St Jeor Equation — Not the Outdated Harris-Benedict
The 1990 Mifflin-St Jeor equation is consistently more accurate for modern adults than the 1919 Harris-Benedict formula. Research shows it predicts measured metabolic rate within 10% for most people.
Understand What 'Eating Too Little' Actually Means
Many people diet below their BMR, which triggers metabolic adaptation and muscle loss. Knowing your BMR helps you set a calorie deficit that promotes fat loss without slowing your metabolism.
Frequently asked questions
If my BMR is 1,800 calories, can I eat only 1,200 calories to lose weight faster?
Eating significantly below your BMR is risky. Your body interprets extreme deficits as starvation and begins breaking down muscle for energy, slowing metabolism. Most nutritionists recommend a deficit of 300–500 calories below your TDEE (not BMR) for sustainable fat loss.
What is the Mifflin-St Jeor BMR formula?
Men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5. Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161. For imperial: convert weight to kg (÷ 2.2046) and height to cm (× 2.54) first.
Why is my BMR different from a fitness app or another calculator?
Different apps use different formulas (Harris-Benedict, Mifflin-St Jeor, Katch-McArdle). Katch-McArdle is most accurate if you know your lean body mass, but requires a body fat measurement. For most people, Mifflin-St Jeor gives the best estimate with just height, weight, age, and sex.
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