Basal Metabolic Rate (BMR) Calculator

What is basal metabolic rate?

Your body uses energy for circulation, breathing, tissue maintenance and other essential functions even when you are not moving. Basal metabolic rate describes this expenditure under specific measurement conditions. Online BMR equations do not perform a laboratory measurement: they estimate resting energy from age, height, weight and sex.

The distinction matters. A result of 1,370 kcal does not mean you should eat exactly 1,370 calories all day. Activity and daily life change total needs. The daily calorie calculator is the tool for exploring food-energy scenarios.

The Mifflin–St Jeor calculation

The main result uses the Mifflin–St Jeor resting energy equation. Weight is in kilograms, height in centimetres and age in years. Pounds and inches are converted before calculation.

Female equation: 10 × kg + 6.25 × cm − 5 × age − 161.
Male equation: 10 × kg + 6.25 × cm − 5 × age + 5.

A woman aged 30 at 165 cm and 65 kg has an estimate of 1,370 kcal/day. A woman aged 60 at 150 cm and 45 kg has an estimate of about 927 kcal/day. The second number is neither an eating recommendation nor a diagnosis of impaired metabolism. The tool does not subtract 500 calories from it to produce a diet target.

BMR versus TDEE

TDEE is total daily energy expenditure. Here resting energy is multiplied by your selected activity factor, from 1.20 to 1.90, to show a secondary maintenance estimate. The factor approximates work, walking, household movement and usual training together.

Multiplying the example of 1,370 kcal by 1.55 gives about 2,124 kcal. Entering the same details and activity level in the calorie calculator gives the same maintenance estimate. This page owns the question of resting expenditure and methods; the calorie page focuses on maintenance and weight-change scenarios.

Comparing Harris–Benedict and Katch–McArdle

The comparison section shows revised Harris–Benedict (1984). If you know your body-fat percentage, the optional field adds a Katch–McArdle estimate based on fat-free mass: 370 + 21.6 × fat-free kilograms. An inaccurate body-fat input affects that estimate too.

The equations are displayed separately. Their average is not assumed to be more accurate. No equation measures your entire routine, medical history or body characteristics. A tape-based body-fat calculation can provide only an approximate input.

Slow metabolism and metabolic age

A low calculated BMR does not diagnose a thyroid condition or “slow metabolism.” A smaller body can also produce a lower estimate. Symptoms and clinical findings need separate assessment; this calculator does not generate a test or supplement list from the number alone.

Some devices report metabolic age by comparing an estimated expenditure with their own reference data. This calculator does not produce metabolic age. Consistent measurement and sustainable habits are more useful than changing an age input to seek a younger-looking result.

Age, muscle and daily habits

Energy expenditure changes across life, but not by one fixed annual percentage for everyone. Research on expenditure across the human life course describes a more complex age pattern. Muscle matters, but it is not the only contributor to resting expenditure.

Consider daily movement, sleep and adequate nutrition together. The muscle-building guide provides training-related context. During pregnancy, breastfeeding or prescribed medical nutrition care, a general adult equation should not be used as an individual target.