Mifflin-St Jeor & Katch-McArdle

BMR Calculator

Find out how many calories your body burns at complete rest. Results update as you type.

Mifflin-St Jeor · Harris-Benedict · Katch-McArdle comparison
Your gender
Your height
Your weight
Your BMR
Mifflin-St Jeor
—
kcal / day
Calories burned at complete rest
Harris-Benedict
—
kcal / day
Revised 1984 formula
Difference
—
kcal / day
Between the two formulas
TDEE estimate (moderately active) — BMR × 1.55 — use TDEE Calculator for exact value
Using the Mifflin-St Jeor equation
Results are estimates for informational purposes only. Not medical advice. Consult a healthcare professional for personalized guidance.

What is BMR?

Basal Metabolic Rate (BMR) is the number of calories your body requires to carry out its most basic life-sustaining functions while at complete rest — breathing, blood circulation, cell production, nutrient processing, and temperature regulation. BMR typically accounts for 60–75% of your total daily calorie expenditure.

The Mifflin-St Jeor Equation

This calculator uses the Mifflin-St Jeor equation by default — widely regarded as the most accurate formula for estimating BMR in healthy adults. Published in 1990, it has been validated in numerous studies against measured metabolic rates.

Male: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Female: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

Katch-McArdle (if you know your body fat %)

If you know your body fat percentage, this formula uses lean body mass for a more personalized estimate — particularly useful for athletes or those with higher-than-average muscle mass.

Lean Body Mass = weight kg × (1 − body fat% / 100)
BMR = 370 + (21.6 × lean body mass kg)
Example:

25-year-old female, 165 cm, 60 kg:

BMR = (10 × 60) + (6.25 × 165) − (5 × 25) − 161 = 600 + 1,031 − 125 − 161 = 1,345 kcal/day

How BMR Connects to Your TDEE

Your BMR is just the starting point. To find how many calories you actually burn each day, multiply your BMR by an activity factor to get your Total Daily Energy Expenditure (TDEE).

TDEE = BMR × Activity Factor

Sedentary (little/no exercise) → × 1.2
Lightly Active (1–3 days/week) → × 1.375
Moderately Active (3–5 days/week) → × 1.55
Very Active (6–7 days/week) → × 1.725
Athlete (twice daily) → × 1.9

Use the TDEE Calculator to get your complete daily calorie estimate based on your activity level.

Related Calculators

TDEE Calculator
Multiply your BMR by an activity factor to get your Total Daily Energy Expenditure.
Calorie Deficit Calculator
Use your BMR as the floor — then build a safe deficit above it for steady fat loss.
Macro Calculator
Once you know your BMR and TDEE, split your calories into protein, carbs, and fat targets.
Body Fat Calculator
Body composition affects your BMR — higher muscle mass raises your resting calorie burn.
TDEE vs BMR — What's the Difference?
A clear explanation of how BMR and TDEE relate, and which number to use for your goals.
Our Methodology
See the Mifflin-St Jeor equation and data sources behind every calculator on this site.

Frequently Asked Questions

What is BMR?+
BMR stands for Basal Metabolic Rate — the calories your body burns at complete rest to maintain basic life functions like breathing, circulation, and cell production. It typically accounts for 60–75% of total daily energy expenditure.
How is BMR calculated?+
BMR is calculated using the Mifflin-St Jeor equation. For men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5. For women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161. If you know your body fat %, the Katch-McArdle formula (BMR = 370 + 21.6 × lean mass kg) may be more accurate.
What is the difference between BMR and TDEE?+
BMR is calories burned at rest. TDEE (Total Daily Energy Expenditure) is your full daily burn including all activity and exercise. TDEE = BMR × activity factor, and is always higher than BMR.
Is BMR the same as resting metabolic rate?+
They are similar but not identical. BMR is measured under strict fasting and rest conditions. RMR (Resting Metabolic Rate) is measured under less restrictive conditions and is typically 10–20% higher. Most online calculators estimate RMR rather than true BMR.