Free Online BMR Calculator

1. Pick metric or imperial units.
2. Enter weight, height, age and select biological sex.
3. Read your estimated BMR in kcal/day.
4. Pair with the TDEE calculator to factor in your activity level.

Basal Metabolic Rate (BMR) is the energy your body needs to keep the lights on: breathing, circulation, cell repair, brain activity. It accounts for 60–70% of a typical person's daily expenditure. Knowing your BMR is the first step before figuring out a maintenance calorie target (TDEE) or planning a deficit or surplus.

The Mifflin-St Jeor equation, published in 1990, is widely considered the most accurate general-population formula. It takes weight in kilograms, height in centimetres, age in years and biological sex, and returns kilocalories per day. The older Harris-Benedict and Katch-McArdle equations exist; for most people the differences are small. People starting a structured diet, athletes setting calorie targets and anyone tracking macros use BMR as the starting figure.

BMR is a population-level estimate. Real metabolism varies by ±10% from person to person due to muscle mass, thyroid function, medication and genetic factors. This is informational only and not medical advice — verify with a qualified professional for important decisions.