BMR Calculator
Calculate Basal Metabolic Rate (BMR)
About the BMR Calculator
Your basal metabolic rate is the number of calories your body burns at complete rest just to keep you alive — breathing, circulating blood, maintaining temperature. This calculator estimates it using the Mifflin-St Jeor equation, the modern standard, from your sex, age, weight, and height.
BMR is the starting point for any calorie plan: it is the floor below which you should rarely eat, and the base that activity is added to in order to find your full daily needs. Anyone setting a weight-loss, maintenance, or muscle-gain target uses it as the anchor number before factoring in exercise.
How to Use the BMR Calculator
- Select your sex.
- Enter your age in years.
- Enter your weight in kilograms.
- Enter your height in centimeters.
- Read your BMR in calories per day, then carry it into a TDEE calculator to factor in activity.
Why Use ToolForge’s BMR Calculator
- It uses the Mifflin-St Jeor equation, which research has found more accurate for most people than the older Harris-Benedict formula.
- It asks only for the four inputs the equation actually needs — sex, age, weight, height — keeping it fast and free of guesswork.
- The result is a clean daily calorie figure ready to feed into activity and goal calculations.
- It calculates locally and instantly, so your body metrics never leave your device.
Frequently Asked Questions
What is the difference between BMR and TDEE?
BMR is the calories you burn at complete rest. TDEE (total daily energy expenditure) is BMR multiplied by an activity factor to include movement and exercise. BMR is the baseline; TDEE is the fuller picture of what you burn in a typical day.
Why does the Mifflin-St Jeor equation matter?
It is the equation this calculator uses because studies have shown it predicts resting metabolic rate more accurately for the general population than older formulas. It bases the estimate on sex, age, weight, and height.
Should I eat at my BMR to lose weight?
Generally no. Eating below your BMR for long periods is not advised, because it is the energy your body needs at rest. Weight loss is usually pursued by eating below your TDEE — your activity-adjusted needs — not below your BMR.
Does BMR change over time?
Yes. BMR tends to decline with age and changes with weight and body composition — more muscle raises it, and significant weight loss lowers it. Recalculate periodically as your stats change to keep your calorie targets accurate.
