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BMR Calculator

Free BMR calculator — your basal metabolic rate and daily calorie needs using the Mifflin-St Jeor and Harris-Benedict equations.

Age (years)

Height (cm)

Weight (kg)

Activity Level

⚠️ Please enter a valid age, height (cm), and weight (kg).

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Everyday Uses

Right-sizing your diet

Your BMR is the floor of your calorie needs — knowing it stops you from choosing a crash diet that's too aggressive.

Understanding metabolism

See how age, size, and sex drive the calories you burn just existing — and why needs change over time.

Fixing fitness app numbers

Apps guess your burn rate. Enter a properly calculated BMR to make their targets meaningful.

Breaking plateaus

Weight loss stalled? Recalculate — a lighter body has a lower BMR, so your old calorie target may now be maintenance.

What an equation can and cannot know

These formulas estimate from height, weight, age and sex. Measured rates scatter around them by a meaningful margin, so the output is a starting point to adjust from, not a fact about you.

It is most of the daily total

For someone with a desk job, basal metabolism accounts for the largest share of energy used in a day — considerably more than deliberate exercise contributes.

Frequently Asked Questions

What is Basal Metabolic Rate (BMR)?

BMR is the number of calories your body burns at complete rest to sustain vital functions — breathing, circulation, temperature regulation, cell repair, and organ function. It accounts for 60–75% of total daily calorie burn for most people. A typical adult BMR is 1,400–1,800 kcal/day for women and 1,600–2,200 kcal/day for men, depending on age, height, and weight.

Which BMR formula is most accurate — Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle?

Mifflin-St Jeor (1990) is the most accurate for the general population — validated in multiple studies and recommended by the Academy of Nutrition and Dietetics. Harris-Benedict (1919, revised 1984) tends to overestimate by 5–15%. Katch-McArdle is most accurate if you know your lean body mass — ideal for athletes with low body fat.

How do age and muscle mass affect BMR?

BMR decreases approximately 1–2% per decade after age 20, primarily due to muscle loss (sarcopenia). A 60-year-old has roughly 10–15% lower BMR than a 20-year-old at the same weight. Building and maintaining muscle mass through resistance training counteracts this decline — each kilogram of muscle burns about 13 kcal/day at rest.

What is the difference between BMR and RMR?

BMR is measured under very strict conditions (fasted, at complete rest after sleep, thermoneutral environment). Resting Metabolic Rate (RMR) is measured under looser conditions and runs 10–20% higher than BMR. Most online calculators actually estimate RMR, not true BMR. In practice, the distinction rarely matters — both are used interchangeably to estimate resting calorie needs.

Can I increase my BMR?

Yes — the most effective way is to increase lean muscle mass through progressive resistance training, as muscle is metabolically more active than fat. High-intensity interval training (HIIT) also creates a post-exercise oxygen consumption (EPOC) effect that elevates metabolism for 12–48 hours. Adequate protein intake (1.6–2.2 g/kg/day) prevents muscle loss and supports metabolic rate.

How to calculate BMR

This uses the Mifflin-St Jeor equation, the one most clinical guidance now prefers: (10 × kg) + (6.25 × cm) − (5 × age), then +5 for men and −161 for women. BMR is what you burn at complete rest — daily needs are BMR multiplied by an activity factor.

BMR examples

Man, 80 kg, 180 cm, 30: 1,780 kcal/day
Woman, 65 kg, 165 cm, 30: 1,370 kcal/day
Man, 70 kg, 175 cm, 40: 1,599 kcal/dayTen years older and 10 kg lighter costs about 180 kcal a day.

BMR vs TDEE

BMR is rest only. Total daily energy expenditure multiplies it by activity: about 1.2 sedentary, 1.55 moderately active, 1.9 very active. A 1,780 kcal BMR becomes roughly 2,760 kcal a day at moderate activity. These are population averages, not a measurement of you — individuals vary by 10% or more either way, and a dietitian can measure it properly.