About the BMR Calculator
Your basal metabolic rate is the energy your body burns just to stay alive — breathing, circulation, cell repair — before you take a single step. This BMR calculator estimates it with the Mifflin-St Jeor equation, the formula most dietitians favour today. Enter your weight, height, age and sex, in either metric or imperial units, and your BMR appears immediately in calories per day.
BMR is the foundation of any calorie plan: everything you burn on top of it comes from movement, exercise and digestion. Knowing your baseline stops you guessing when setting daily targets for weight loss, maintenance or muscle gain. Imperial entries are converted to metric automatically behind the scenes, the result updates the instant you type, and none of your personal figures ever leave your browser.
Features
- Uses the trusted Mifflin-St Jeor equation
- Metric and imperial inputs, converted automatically
- Separate formula constants for men and women
- Result shown in calories (kcal) per day
- Pairs with the calorie calculator for TDEE
- Free, instant and fully in-browser
How to calculate your BMR
- Select metric or imperial units and your sex.
- Enter your weight and height.
- Enter your age in years.
- Read your BMR in calories per day.
Frequently asked questions
What exactly is BMR?
Basal metabolic rate is the number of calories your body needs per day at complete rest to run essential functions — breathing, heartbeat, temperature regulation and cell maintenance. For most people it accounts for 60 to 70 percent of total daily energy use, making it the largest slice of the calorie budget.
Which formula does this BMR calculator use?
It uses the Mifflin-St Jeor equation: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 for men, or − 161 for women. Imperial inputs are converted to kilograms and centimetres before the formula runs, so both unit systems always produce exactly the same daily calorie figure.
Why Mifflin-St Jeor instead of Harris-Benedict?
The Harris-Benedict equation dates from 1919 and tends to overestimate modern resting metabolism. Mifflin-St Jeor, published in 1990, proved more accurate in validation studies and is the equation recommended by the Academy of Nutrition and Dietetics, which is why this calculator uses it.
What is the difference between BMR and TDEE?
BMR is your burn at complete rest; TDEE (total daily energy expenditure) adds everything else — walking, exercise, fidgeting and digesting food. TDEE is estimated by multiplying BMR by an activity factor between 1.2 and 1.9. Tooldoodle's calorie calculator does that next step for you.
How accurate is a BMR estimate?
Any equation is an estimate: individual metabolisms vary with genetics, muscle mass, hormones and health conditions, typically by around 10 percent either way. Treat the number as a starting point, not a medical measurement, and consult a doctor or registered dietitian before making significant dietary changes.