Your Basal Metabolic Rate (BMR) represents the minimum calories your body needs to maintain basic functions like breathing, circulation, and cell production while at complete rest. This BMR calculator uses scientifically validated formulas to help you understand your metabolism and plan your nutrition for weight loss, maintenance, or muscle gain.
Input your gender, age, weight, and height. Choose metric (kg/cm) or imperial (lb/ft) units.
Choose your typical weekly exercise frequency to calculate TDEE accurately.
If known, enter your body fat percentage for the more accurate Katch-McArdle calculation.
Select whether you want to lose weight, maintain, or build muscle to get your target calories.
The Mifflin-St Jeor equation is considered the most accurate for calculating BMR. TDEE (Total Daily Energy Expenditure) is calculated by multiplying BMR by an activity factor.
BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + s
BMR accounts for about 60-75% of your total daily calorie expenditure - it's the calories you burn just being alive.
The Mifflin-St Jeor formula is generally more accurate for modern populations than the older Harris-Benedict equation.
To lose weight, create a calorie deficit of 500-750 calories below your TDEE for safe, sustainable weight loss of 0.5-1kg per week.
Never eat below your BMR for extended periods - this can slow your metabolism and lead to muscle loss.
Your BMR naturally decreases with age (about 2% per decade after 20), which is why maintaining muscle mass is important.
If you know your body fat percentage, the Katch-McArdle formula provides the most accurate BMR calculation.
Your BMR is the foundation of your daily calorie needs. Understanding it helps you make informed decisions about nutrition, weight management, and fitness goals.
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulation, cell production, and nutrient processing while at complete rest.
It represents 60-75% of your total daily energy expenditure.
The Mifflin-St Jeor equation (1990) is the most widely recommended formula:
This formula is preferred by dietitians and nutritionists.
While BMR measures calories burned at rest, TDEE (Total Daily Energy Expenditure) includes all calories burned through activity. TDEE = BMR × Activity Factor.
For weight loss, create a deficit from TDEE, not BMR. Never eat below your BMR consistently.
Multiply your BMR by:
These factors convert BMR to TDEE.
The original Harris-Benedict formula (1918) tends to overestimate calories by 5-10%:
Still useful for comparison.
If you know your body fat percentage, Katch-McArdle is most accurate: BMR = 370 + 21.6 × Lean Body Mass (kg).
This formula accounts for body composition, making it ideal for athletes and those who've measured their body fat.
Basal metabolic rate (BMR) and resting metabolic rate (RMR) both measure calories burned at rest, but under different conditions.
BMR is measured under strict laboratory conditions — fully rested, fasted, and awake after overnight sleep — while RMR is measured under less restrictive conditions and runs a few percent higher.
In everyday use the terms are often interchanged; the Mifflin-St Jeor equation used here (BMR ≈ 1780 kcal for an 80 kg, 180 cm, 30-year-old man) technically estimates BMR. The distinction rarely matters for calorie planning.
Your BMR is the calorie floor your body needs at complete rest; multiplying it by an activity factor gives total daily energy expenditure (TDEE). For the example man, a moderate activity factor of 1.55 gives a TDEE near 2759 kcal.
To lose weight, eat below TDEE — a deficit of about 500 kcal/day yields roughly one pound per week, per the Academy of Nutrition and Dietetics, and the resulting fat loss often improves heart-health markers you can track with a cholesterol calculator.
Never eat below your BMR long-term, as it can slow metabolism and cost muscle.
BMR is driven mostly by lean body mass — muscle burns more at rest than fat — which is why men typically have higher BMRs than women of the same weight, and why strength training raises BMR over time.
Age, height, genetics, hormones (thyroid), and body temperature also matter.
The Katch-McArdle formula, which uses lean mass, can be more accurate for lean, muscular individuals than weight-based equations. Crash dieting lowers BMR as the body conserves energy.
BMR gradually falls with age, largely because adults tend to lose muscle mass (sarcopenia) and gain fat unless they train to preserve it. This is why the same eating habits that maintained weight at 25 can cause gradual gain at 45.
The decline is not inevitable in magnitude: resistance training and adequate protein blunt muscle loss and keep BMR higher. Recalculating BMR every few years, and after major weight changes, keeps calorie targets accurate.
Frequent mistakes include:
People also expect the estimate to be exact — predictive equations carry a margin of error of roughly ±10%. Use BMR as a starting point, track results over a few weeks, and adjust intake based on actual weight change.
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All formulas verified against official standards.