Health & Fitness

BMR Calculator

Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the three most accurate scientific formulas. Get your personalized daily calorie targets for any goal.

%
Essential
♂ 2–5%♀ 10–13%
Athletic
♂ 6–13%♀ 14–20%
Fitness
♂ 14–17%♀ 21–24%
Average
♂ 18–24%♀ 25–31%
Obese
♂ 25%+♀ 32%+

Activity Multiplier Reference

The Harris-Benedict activity factors used to calculate TDEE from BMR.

Activity Level Factor Description Example
Sedentary ×1.2 Little/no exercise Office worker, minimal walking
Lightly Active ×1.375 Exercise 1–3 days/week Walk 30 min daily, light gym
Moderately Active ×1.55 Exercise 3–5 days/week Gym 4×/week, moderate intensity
Very Active ×1.725 Hard exercise 6–7 days/week Daily gym + physical job
Extra Active ×1.9 Very hard exercise + physical job Athlete, construction worker, 2× daily training

BMR, TDEE & Calorie Needs: Complete Guide

Your Basal Metabolic Rate (BMR) is the foundation of all nutrition planning. It tells you the minimum calories your body needs to sustain life — your heart beating, your lungs breathing, your cells replicating. Understanding your BMR and Total Daily Energy Expenditure (TDEE) eliminates the guesswork from dieting and allows you to set precise calorie targets based on science rather than generic advice.

Which BMR Formula is Most Accurate?

The Mifflin-St Jeor equation (1990) is considered the gold standard for most people. A meta-analysis by Frankenfield et al. (2005) found it predicted resting energy expenditure within 10% in 82% of non-obese individuals — outperforming Harris-Benedict and Owen equations. If you know your body fat percentage, the Katch-McArdle formula is even more accurate because it calculates from lean mass directly, accounting for the fact that muscle burns more calories than fat.

How to Use BMR for Weight Loss

Calculate your TDEE, then create a moderate calorie deficit. A 500-calorie daily deficit theoretically produces 0.5 kg (1 lb) of weight loss per week (since 1 kg of fat ≈ 7,700 calories). In practice, aim for 0.5–1% of body weight loss per week to preserve muscle mass. Never drop below 1,200 calories (women) or 1,500 calories (men) without medical supervision — extreme deficits slow your metabolism through adaptive thermogenesis.

BMR and Muscle Building

Building muscle requires a caloric surplus above TDEE. A lean bulk of 250–500 extra calories per day minimizes fat gain while supporting muscle protein synthesis. Natural muscle-building rates are limited: beginner men may gain 1–1.5 kg of muscle per month, intermediate 0.5–1 kg, advanced 0.25–0.5 kg. Women gain at roughly half these rates. Higher surpluses beyond 500 calories primarily add body fat, not muscle.

Frequently Asked Questions

BMR is the number of calories your body burns at complete rest to maintain basic life functions — breathing, circulation, cell production, and organ function. It represents the minimum energy your body needs to survive if you did nothing but lie in bed all day. BMR accounts for 60–75% of total daily calorie expenditure for most people.
BMR is your calorie burn at complete rest. TDEE (Total Daily Energy Expenditure) is your total daily calorie burn including all physical activity. TDEE = BMR × Activity Multiplier. For example, if your BMR is 1,600 calories and you're moderately active, your TDEE ≈ 1,600 × 1.55 = 2,480 calories per day. This is what you need to eat to maintain your current weight.
The Mifflin-St Jeor equation (1990) is the most accurate BMR formula for most people. For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161. It outperforms the older Harris-Benedict equation in predicting resting energy expenditure in multiple validation studies.
The original Harris-Benedict equation (1919, revised 1984) calculates BMR based on weight, height, and age. Revised Men: BMR = (13.397 × kg) + (4.799 × cm) − (5.677 × age) + 88.362. Revised Women: BMR = (9.247 × kg) + (3.098 × cm) − (4.330 × age) + 447.593. It was the gold standard for decades but the Mifflin-St Jeor is now preferred for non-obese individuals.
The Katch-McArdle formula calculates BMR from lean body mass (fat-free mass) rather than total weight: BMR = 370 + (21.6 × lean mass in kg). This is the most accurate formula if you know your body fat percentage, as it accounts for the fact that muscle burns more calories than fat. Athletes and bodybuilders benefit most from this formula.
A safe calorie deficit for weight loss is 500–750 calories per day below your TDEE, resulting in approximately 0.5–0.75 kg (1–1.5 lb) of weight loss per week. Never eat below your BMR for extended periods — this causes muscle loss and metabolic slowdown. The minimum recommended intake is 1,200 calories/day for women and 1,500 calories/day for men.
To build muscle (bulk), eat 250–500 calories above your TDEE per day. A moderate surplus minimizes fat gain while providing enough energy for muscle growth. Combined with progressive resistance training, this results in approximately 0.25–0.5 kg (0.5–1 lb) of muscle per week for natural trainees. Beginners may gain faster.
Yes. BMR decreases by approximately 1–2% per decade after age 20. This is mainly due to muscle mass loss (sarcopenia) — after 30, sedentary adults lose 3–5% of muscle mass per decade. Regular strength training counters this by preserving metabolically active muscle tissue. Women also experience a significant drop in BMR during and after menopause due to hormonal changes.
Men generally have a higher BMR than women of the same weight and height because men carry more lean muscle mass and less body fat. Muscle tissue burns approximately 4–7 times more calories than fat tissue at rest. A man and woman of the same total weight might have a BMR difference of 100–300 calories per day due to body composition differences.
Muscle mass: more muscle = higher BMR. Genetics: some people are naturally faster/slower metabolizers. Thyroid hormones: hyperthyroidism raises BMR, hypothyroidism lowers it. Temperature: BMR increases in cold environments. Pregnancy: raises BMR 15–20%. Fever: raises BMR ~7% per degree C above normal. Crash dieting: can lower BMR by 15–30% through adaptive thermogenesis.
Step 1: Calculate your BMR using our calculator. Step 2: Multiply by your activity factor to get TDEE. Step 3: To lose weight, eat 300–500 calories below TDEE. To maintain, eat at TDEE. To gain muscle, eat 250–500 above TDEE. Step 4: Track for 2–3 weeks and adjust — if you're not seeing expected changes, your TDEE estimate may need refinement.
They are often used interchangeably but technically differ. BMR is measured under very strict conditions: complete rest for 12 hours after sleep, 12 hours fasted, in a thermoneutral environment (22°C). RMR (Resting Metabolic Rate) has less strict conditions and is typically 10–20% higher than true BMR. Most online calculators and "BMR calculators" actually calculate RMR.