BMR Calculator
Find out how many calories your body burns at rest. Compare three proven scientific formulas side by side.
How to use this calculator
Enter your height, weight, age, and gender using the sliders — your BMR updates instantly. The Mifflin-St Jeor equation is highlighted as recommended since it's the most validated for modern adults. Optionally enter your body fat percentage (tap the ? button to learn how to find it) to unlock the Katch-McArdle formula, which is the most accurate method for athletes and muscular individuals.
Understanding your BMR
BMR (Basal Metabolic Rate) is the number of calories your body burns just to stay alive — breathing, circulation, cell repair — if you were completely at rest for 24 hours. It's the foundation of all calorie calculations. Your actual daily calorie burn (TDEE) is higher once you add movement and activity. The three formulas often give slightly different results because they were developed using different study populations. Mifflin-St Jeor (1990) is the most widely validated for modern adults.
Frequently asked questions
BMR formula comparison
Three formulas are used to calculate BMR, each developed from different study populations. The Mifflin-St Jeor (1990) is the most validated for modern adults. Harris-Benedict (revised 1984) is older and slightly less accurate. Katch-McArdle is the most precise when body fat percentage is known.
| Formula | Year | Best for | Typical accuracy |
|---|---|---|---|
| Mifflin-St Jeor | 1990 | General adults (recommended) | Within 10% for most people |
| Harris-Benedict (revised) | 1984 | General use; older formula | Overestimates by ~5% on average |
| Katch-McArdle | 1996 | Athletes; requires body fat % | Most accurate when BF% is known |
What affects your BMR?
BMR is not fixed — it changes with body composition, age, hormones, and health status. Understanding what drives your metabolic rate helps you manage it more effectively over time.
- ·Muscle mass — skeletal muscle burns 6x more calories at rest than fat tissue; building muscle is the most effective way to raise BMR
- ·Age — BMR declines approximately 1–2% per decade after age 30, primarily due to muscle loss (sarcopenia)
- ·Sex — men have higher BMR than women at the same weight due to greater muscle mass and lower body fat percentage
- ·Thyroid function — thyroid hormones directly regulate metabolic rate; both hypo- and hyperthyroidism significantly affect BMR
- ·Body size — taller, heavier people have higher BMR in absolute terms
- ·Calorie restriction — prolonged severe deficits lower BMR by 10–20% as the body adapts to conserve energy
- ·Sleep — chronic sleep deprivation reduces metabolic rate and increases hunger hormones (ghrelin)
Average BMR by age and sex
These are approximate average BMR values from population data. Individual values vary widely based on muscle mass and body composition.
| Age group | Average BMR — Women | Average BMR — Men |
|---|---|---|
| 18–29 | 1,480–1,550 cal/day | 1,850–1,950 cal/day |
| 30–39 | 1,440–1,510 cal/day | 1,800–1,900 cal/day |
| 40–49 | 1,390–1,460 cal/day | 1,730–1,830 cal/day |
| 50–59 | 1,340–1,410 cal/day | 1,660–1,760 cal/day |
| 60–69 | 1,290–1,360 cal/day | 1,590–1,690 cal/day |
| 70+ | 1,240–1,310 cal/day | 1,520–1,620 cal/day |
How to raise your BMR
Because BMR represents 60–70% of total calorie burn, even small increases compound significantly over time. Muscle is the most powerful lever — each pound of muscle burns an estimated 6–10 extra calories per day at rest, compared to roughly 2 cal/day for a pound of fat.
- ·Build muscle through progressive resistance training — the single most effective way to raise resting metabolism long-term
- ·Eat sufficient protein (1.6–2.2g/kg) to support muscle maintenance and growth
- ·Avoid crash dieting — deficits over 1,000 cal/day trigger metabolic adaptation that can suppress BMR by 10–20%
- ·Prioritize sleep (7–9 hours) — growth hormone peaks during deep sleep and is essential for muscle repair
- ·Stay adequately hydrated — even mild dehydration can reduce metabolic efficiency