BMR Calculator
Estimate your Basal Metabolic Rate — the calories your body burns at rest.
So funktioniert's
Basal Metabolic Rate (BMR) is an estimate of how many calories your body burns in a day doing absolutely nothing — no exercise, no digestion of food, just the energy needed to keep your heart beating, lungs breathing, and cells functioning at complete rest.
This calculator uses the Mifflin-St Jeor equation, developed in 1990 and widely considered the most accurate BMR formula in current use. For men, it's BMR = 10×weight(kg) + 6.25×height(cm) − 5×age(years) + 5. For women, the same formula subtracts 161 instead of adding 5.
For example, a 30-year-old woman weighing 65 kg at 165 cm has a BMR of (10×65) + (6.25×165) − (5×30) − 161 = 650 + 1031.25 − 150 − 161 ≈ 1,370 calories per day.
Mifflin-St Jeor replaced the older Harris-Benedict equation (from 1919, revised in 1984) as the preferred formula because later research found it more accurately predicted measured BMR across a wide range of body types — though no formula-based estimate perfectly matches a lab measurement for every individual.
BMR varies with more than just the four inputs this formula uses: muscle mass increases BMR (muscle burns more calories at rest than fat tissue), genetics play a role, and certain medical conditions like thyroid disorders can meaningfully raise or lower it. Treat the result as a solid estimate, not a lab-measured value.
BMR is the foundation for calculating full daily calorie needs — multiplying it by an activity factor (to account for movement and exercise beyond resting) gives your Total Daily Energy Expenditure, which the Calorie Calculator computes directly.
A separate formula, the Katch-McArdle equation, estimates BMR from lean body mass instead of total weight, age, and sex — it can be more accurate for people with an unusually high or low muscle-to-fat ratio, but requires already knowing your body fat percentage (from the Body Fat Calculator) as an input, which is why Mifflin-St Jeor remains the more commonly used general-purpose formula.
How is BMR different from calorie needs?
BMR is calories burned at complete rest; total calorie needs multiply BMR by an activity factor.
What is the Katch-McArdle formula, and how is it different?
It estimates BMR from lean body mass rather than total weight, age, and sex — potentially more accurate for very muscular or very lean individuals, but it requires knowing your body fat percentage first.
What is the Mifflin-St Jeor equation?
A formula developed in 1990 that estimates BMR from weight, height, age, and sex — currently considered the most accurate widely-used BMR formula, replacing the older Harris-Benedict equation.
Why does BMR differ between men and women at the same weight and height?
The formula subtracts a larger constant for women, reflecting that women generally have a higher proportion of body fat to muscle on average, and muscle tissue burns more calories at rest than fat.
Does more muscle mean a higher BMR?
Yes — muscle tissue burns more calories at rest than fat tissue, so two people at the same weight but different muscle mass can have meaningfully different actual BMRs, even though this formula doesn't measure muscle mass directly.
Can medical conditions affect BMR?
Yes — thyroid disorders in particular can significantly raise or lower metabolic rate; if your real-world calorie needs seem very different from this estimate, it's worth discussing with a healthcare provider.
How accurate is a formula-based BMR compared to a lab test?
Formulas like Mifflin-St Jeor are good population-level estimates but won't perfectly match an individual's actual measured BMR (from indirect calorimetry) — they're a solid starting point, not a substitute for direct measurement.
Why did Mifflin-St Jeor replace the Harris-Benedict equation?
Later validation studies found Mifflin-St Jeor predicted measured BMR more accurately across diverse body types than the older Harris-Benedict formula, leading most nutrition professionals to prefer it today.
Does BMR decrease with age?
Yes — the formula subtracts more as age increases, reflecting the general trend of metabolism gradually slowing with age, largely due to natural muscle loss over time.
What should I do with my BMR result?
Use it as the starting point for the Calorie Calculator, which multiplies BMR by your activity level to estimate your full daily calorie needs for maintaining, losing, or gaining weight.