BMR Calculator

--Mifflin-St Jeor (kcal/day)
--Harris-Benedict (kcal/day)

TDEE Estimates (Mifflin-St Jeor)

Activity LevelMultiplierCalories/day

What Is Basal Metabolic Rate (BMR)?

Your Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions — such as breathing, circulation, and cell production — while completely at rest for 24 hours. It represents the minimum energy required to keep you alive, accounting for roughly 60–75% of total daily calorie expenditure.

Mifflin-St Jeor vs Harris-Benedict Formula

Two widely used equations estimate BMR:

  • Mifflin-St Jeor (1990): Generally considered more accurate for modern populations. For men: BMR = 10W + 6.25H − 5A + 5; For women: BMR = 10W + 6.25H − 5A − 161.
  • Harris-Benedict (1919, revised 1984): One of the oldest formulas, still widely used. It tends to overestimate by about 5% compared to Mifflin-St Jeor.

Research published in the Journal of the American Dietetic Association found the Mifflin-St Jeor equation to be most accurate in the general population, though individual variation is always present.

BMR vs TDEE — What Is the Difference?

BMR is your calorie need at complete rest. Total Daily Energy Expenditure (TDEE) multiplies your BMR by an activity factor to account for exercise and daily movement. To lose weight, you create a calorie deficit below your TDEE; to gain weight, you eat above it.

Using BMR in a Diet Plan

Never eat below your BMR long-term — doing so triggers adaptive thermogenesis and muscle catabolism. A sensible starting point is 500 kcal below TDEE for gradual fat loss (~0.5 kg/week) or 300–500 kcal above TDEE for lean muscle gain.

Frequently Asked Questions

Does BMR change with age?
Yes. BMR generally declines about 1–2% per decade after age 20, largely due to loss of lean muscle mass. Regular resistance training can help preserve muscle and slow this decline.
Why do men have a higher BMR than women?
Men typically have more lean muscle mass and less body fat than women of the same weight, and muscle tissue burns more calories at rest than fat tissue, resulting in a higher BMR.
Can I increase my BMR?
Building muscle through resistance training is the most effective way to raise your BMR. Each kilogram of muscle burns approximately 13 kcal/day at rest, compared to only about 4.5 kcal/day per kilogram of fat.
Are these formulas accurate?
These equations provide estimates within 10–15% for most people. Individual factors like genetics, hormonal status (thyroid function), and body composition can cause actual BMR to differ from the prediction.