BMR Calculator

Estimate the calories your body may use at rest over 24 hours.

Age

Sex used in equation Male Female

Weight (kg)

Height (cm)

Please enter valid adult age, height, and weight values.

Estimated BMR

--

calories/day at rest

-- Approx. calories/hour at rest

-- Approx. daily calories per kg

This is a predictive estimate of resting energy needs. It is not a direct metabolic measurement and should not be used as a medical diagnosis or a stand-alone calorie prescription.

BMR Guide

What Is Basal Metabolic Rate?

Basal metabolic rate, or BMR, describes the energy your body needs to support essential life processes over a 24-hour period. These processes include basic cellular activity and functions required to keep the body alive even when you are not exercising.

BMR is only one part of total daily energy expenditure. Physical activity, everyday movement, and the energy used to digest food add to the calories your body uses across the day.

Important: This calculator provides a prediction for general educational use. It does not directly measure your metabolism. Medical conditions, medications, body composition, pregnancy, age-related changes, and other factors can affect actual energy needs.

1

Enter Basic Measurements

The equation uses age, sex, weight, and height to estimate resting energy expenditure.

2

View the Estimate

Your result is shown as estimated calories per day at rest, together with simple hourly and weight-based reference figures.

Calculation Method

How the BMR Calculator Works

This calculator uses the Mifflin–St Jeor predictive equation, published in 1990 to estimate resting energy expenditure in adults. The formula uses body weight in kilograms, height in centimetres, age in years, and a sex-specific constant.

Male estimate = (10 × weight) + (6.25 × height) − (5 × age) + 5

Female estimate = (10 × weight) + (6.25 × height) − (5 × age) − 161

The original study described the equation as a prediction of resting energy expenditure. In everyday calculator use, the result is often presented as a BMR or resting-calorie estimate, but an equation cannot replace a direct metabolic measurement.

BMR vs Daily Calories

BMR Is Not the Same as Your Total Daily Calorie Need

Your BMR represents an estimate of energy use at rest. It does not include all of the energy you use during walking, work, exercise, household activity, or digestion.

Total daily energy expenditure is therefore normally higher than BMR. A calorie intake target should not simply be set equal to your BMR without considering activity, nutrition, health status, and individual circumstances.

A

Age

Age is one of the variables used by the predictive equation, so changing age changes the calculated estimate.

B

Body Size

Height and weight are included because larger bodies generally require more energy to maintain basic functions.

C

Body Composition

The simple equation does not directly measure muscle mass or body-fat percentage, which can contribute to differences between predicted and measured energy expenditure.

D

Health & Physiology

Illness, medicines, hormonal conditions, pregnancy, and other physiological factors may change energy requirements in ways a basic calculator cannot capture.

Accuracy

How Accurate Is a BMR Estimate?

Predictive equations are designed to estimate resting energy expenditure across groups of people. They can be useful when direct measurement is unavailable, but the result for an individual may differ from actual measured metabolism.

Indirect calorimetry is one method used in clinical or research settings to measure resting energy expenditure more directly by assessing respiratory gases. For most people using an online calculator, the result should therefore be treated as an informed estimate rather than an exact metabolic number.

Using the Result

What Can You Do With Your BMR Estimate?

A BMR estimate can help explain the difference between resting energy needs and total daily calorie expenditure. It may also serve as one input in a broader energy-needs calculation that accounts for physical activity.

If your goal involves weight loss, weight gain, sports performance, pregnancy nutrition, or management of a medical condition, personalized guidance may be more appropriate than relying only on a predictive equation.

Frequently Asked Questions

BMR Calculator FAQs

Does BMR include exercise?

No. BMR is intended to represent basic resting energy needs. Exercise and other physical activity contribute additional energy expenditure.

Is BMR the number of calories I should eat?

Not necessarily. BMR is an estimate of resting energy expenditure, not a complete calorie-intake recommendation. Daily energy needs usually include activity and other components.

Why can two people with the same weight have different BMR estimates?

The equation also uses height, age, and sex. In real life, body composition and other physiological differences may further affect measured energy expenditure.

Can I use this BMR calculator during pregnancy?

A general adult predictive calculator does not account for the changing energy and nutritional needs of pregnancy. Individualized prenatal guidance is more appropriate.

Is BMR measured or estimated here?

Estimated. This calculator uses a predictive equation rather than direct metabolic testing.

Sources

Method and Reference Information

The calculation is based on the Mifflin–St Jeor predictive equation for resting energy expenditure. Public-health material also describes basal energy expenditure as the energy needed to support basic metabolic and life processes.

Mifflin–St Jeor Study NCBI Resting Metabolic Rate Table CDC Energy Requirement Overview