What Is BMR? Basal Metabolic Rate Explained (With Formula)

By the CaloriesSnap Editorial Team · Updated August 26, 2026 · Our methodology

Quick answer: BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest, just to keep you alive: breathing, pumping blood, running your brain and organs, and repairing cells. It's usually 60–70% of your total daily burn. Typical values are about 1,200–1,500 kcal/day for women and 1,500–1,900 kcal/day for men.

Where do BMR calories go?

Even lying perfectly still, your organs are working hard. Approximate share of resting energy use:

Organ / tissue	Approx. share of resting energy
Liver	~20%
Brain	~20%
Skeletal muscle	~20%
Heart	~10%
Kidneys	~8%
Everything else (gut, fat tissue, lungs, skin…)	~20%

How to calculate BMR: the Mifflin-St Jeor formula

The Mifflin-St Jeor equation (1990) is considered one of the most accurate everyday formulas for healthy adults and is recommended by the Academy of Nutrition and Dietetics for estimating resting energy needs.

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(y) + 5

Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(y) − 161

Worked example: Omar, 40 years old, 178 cm, 85 kg.

10 × 85 = 850
6.25 × 178 = 1,112.5
5 × 40 = 200
BMR = 850 + 1,112.5 − 200 + 5 = ~1,768 kcal/day

That's what Omar would burn lying in bed all day. His full daily needs (TDEE) are higher. See BMR vs TDEE.

Calculate your BMR instantly

Free BMR calculator with Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle formulas.

Open the BMR Calculator →

Other BMR formulas

Formula	Best for	Note
Mifflin-St Jeor (1990)	Most adults	Usually the default choice
Harris-Benedict (1919, revised 1984)	General use	Older; tends to estimate slightly higher
Katch-McArdle	Lean, athletic people who know their body fat %	Uses lean body mass: 370 + 21.6 × LBM(kg)

Know your body fat? Find your lean mass with the Body Fat Calculator and Lean Body Mass Calculator, then use Katch-McArdle.

What affects your BMR?

Body size: heavier and taller people have higher BMR.
Muscle mass: lean tissue burns more at rest than fat tissue.
Age: BMR declines gradually in older adulthood, partly from muscle loss.
Sex: men tend to have higher BMR on average because of larger body size and more lean mass.
Genetics & hormones: thyroid hormones especially. An underactive thyroid lowers BMR.
Long or severe dieting: BMR falls as you lose weight, and may drop a bit more than expected (adaptive thermogenesis).

Can you "boost" your metabolism?

✅ Works (modestly): strength training to build or keep muscle; eating enough protein, especially while dieting; avoiding very aggressive, prolonged calorie cuts.

❌ Mostly hype: "metabolism-boosting" pills, spicy foods, green tea, or eating many small meals. Effects are tiny or unproven.

Your biggest lever for burning more calories is usually daily movement, not BMR. See what is TDEE.

⚠️ Don't eat below your BMR without guidance. Eating far under your BMR for long periods can make it hard to get enough nutrients, increase muscle loss, and be hard to sustain. If you have a medical condition, are pregnant, or have a history of disordered eating, speak with a doctor or registered dietitian before restricting calories.

Frequently asked questions

What is a normal BMR?

For most adults, BMR falls roughly between 1,200 and 1,500 kcal/day for women and 1,500 and 1,900 kcal/day for men. Your own value depends on your weight, height, age, sex, and body composition.

Should I eat my BMR to lose weight?

Not necessarily. BMR is only your resting burn, not your total daily needs. Most people lose weight eating somewhat below their TDEE, which is usually well above BMR. Eating at or below BMR for long periods is aggressive and may not be appropriate without professional guidance.

Can I increase my BMR?

Modestly. Building muscle through strength training raises BMR slightly, and maintaining muscle during weight loss helps prevent it from dropping. Body weight, age, and genetics have larger effects than anything you can change quickly.

What is the difference between BMR and RMR?

BMR (basal metabolic rate) is measured under strict lab conditions: fasted, fully rested, at a comfortable temperature. RMR (resting metabolic rate) is measured under less strict conditions and is usually slightly higher. For everyday planning, the two terms are used almost interchangeably.

Sources

This article is for general education and is not medical advice. BMR formulas give estimates; your actual value may differ. Consult a qualified healthcare professional before making significant dietary changes. See our medical review policy and disclaimer.