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