BMR Calculator · Practical guide
Mifflin-St Jeor Equation Calculator
Published in 1990, Mifflin-St Jeor is the most reliable BMR formula for healthy adults — usually within 10% of lab measurements.
At a glance
The Equations
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
The calculator above applies these directly and rounds to the nearest calorie, converting pounds and inches automatically if you choose imperial units.
Interactive tool
BMR Calculator
Enter your own values, then compare the result with the examples below.
Daily Calorie Needs by Activity
| Activity Level | Multiplier | Calories / Day |
|---|---|---|
| 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 | -- |
| Super active (physical job/training) | 1.9 | -- |
Worked Example: Woman, 30, 65 kg, 165 cm
- Weight term: 10 × 65 = 650
- Height term: 6.25 × 165 = 1,031.25
- Age term: 5 × 30 = 150
- BMR = 650 + 1,031.25 − 150 − 161 = 1,370.25 ≈ 1,370 kcal/day
Why Mifflin-St Jeor Over the Others
The older Harris-Benedict equation tends to overestimate by 5% or more, and Katch-McArdle needs a measured body fat percentage to work. Mifflin-St Jeor hits within about 10% of measured metabolic rate for most healthy adults using only scale weight, height, and age — which is why the Academy of Nutrition and Dietetics recommends it.
From BMR to Daily Needs
The result panel multiplies your BMR by five activity factors, from 1.2 (sedentary) to 1.9 (physical job or heavy training). For the 1,370 kcal example, that means about 1,644 kcal sedentary and 2,124 kcal with moderate exercise — the numbers that actually drive a meal plan.
Frequently Asked Questions
When was the Mifflin-St Jeor equation developed?
It was published in 1990 by MD Mifflin and ST St Jeor, based on measurements of nearly 500 subjects, and later validated as the best predictive BMR formula for healthy adults.
How accurate is Mifflin-St Jeor?
Typically within about 10% of measured resting metabolism for healthy adults. Accuracy drops for the very lean, very muscular, or severely obese, where Katch-McArdle may do better.
Does the formula work for both metric and imperial?
The equation itself uses kilograms and centimeters. The calculator converts pounds and inches for you when you select imperial units.
Why does the women's formula subtract 161?
The −161 constant (versus +5 for men) reflects average differences in body composition — women carry proportionally more fat and less calorie-hungry lean mass at the same size.