BMR Calculator

What this calculator does

The BMR Calculator estimates basal metabolic rate, the amount of energy the body would use over a day at rest to support functions such as breathing, circulation, temperature regulation, and basic cellular activity.

How to use the calculator step by step

Enter age, sex, height, and weight using the units shown. Calculate the result and distinguish BMR from total daily calorie needs: BMR does not include normal walking, work, exercise, or most daily activity.

How the calculation works

BMR equations combine weight, height, age, and sex using coefficients derived from population data. Common equations include Mifflin-St Jeor and Harris-Benedict variants. Different equations can produce slightly different estimates for the same person.

Worked example and scenario testing

A calculated BMR of 1,550 calories per day means the equation estimates roughly that amount of energy for basic resting functions. It does not mean the person should eat exactly 1,550 calories, because normal daily activity increases total energy expenditure.

How to interpret your result

BMR is best understood as one component of energy expenditure. To estimate maintenance calories, a BMR result is often multiplied by an activity factor.

Accuracy, assumptions, and limitations

The equation does not directly measure metabolism and may be less accurate for people with unusual body composition, very high muscularity, certain medical conditions, pregnancy, or large recent weight changes.

Common mistakes to avoid

Do not confuse BMR with maintenance calories. Another common error is using the wrong height or weight units or selecting an equation result as though it were a laboratory measurement.

Privacy and browser-based calculations

The calculation uses only the values required by the form. Avoid entering identifying or confidential medical information.

Frequently asked questions