Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to keep vital functions running — breathing, circulation, cell production, and temperature regulation. It does not include any activity.

What is the difference between the original and revised equation?

The original Harris-Benedict (1919) formula tends to overestimate calorie needs slightly, especially for overweight individuals. The revised Mifflin-St Jeor (1990) version is generally considered more accurate for modern populations and is recommended by most dietitians.

Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor. It represents the total calories you burn in a day including exercise and daily movement.

How accurate is this calculator?

The Harris-Benedict and Mifflin-St Jeor equations are population-level estimates. Individual variation due to body composition, metabolism, and genetics means actual calorie needs may differ by 10–20%. Use the result as a starting point and adjust based on real-world results.

Which activity level should I choose?

Choose sedentary if you have a desk job and little exercise. Lightly active if you walk or do light exercise 1-3 days/week. Moderately active if you exercise 3-5 days/week. Very active if you do hard exercise 6-7 days/week. Extra active for physically demanding jobs plus daily training.

How many calories should I eat to lose weight?

A common starting point is a 500 calorie/day deficit from your TDEE, which targets roughly 0.5 kg (1 lb) of fat loss per week. Deficits larger than 1000 calories/day are generally not recommended without medical supervision.

Harris-Benedict BMR Calculator

Name: Harris-Benedict BMR Calculator
Availability: InStock
Author: Nham Vu

Enter your age, sex, height, and weight to calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the Harris-Benedict equation.

Your Details

Unit System

Biological Sex

Age (years)

Height (cm)

Weight (kg)

Activity Level

Fill in your details and click Calculate to see your BMR and TDEE.

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Summary

Enter your age, sex, height, and weight to calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the Harris-Benedict equation.

How it works

Enter your biological sex, age, height, and weight.
Select your preferred unit system (metric or imperial).
Choose your typical activity level from sedentary to very active.
The calculator applies both the original Harris-Benedict and revised Mifflin-St Jeor formulas.
Your BMR and TDEE are displayed instantly with a breakdown by goal.

Use cases

Determine daily calorie needs for weight loss or muscle gain.
Compare original vs. revised Harris-Benedict equation results.
Set a science-based calorie target before starting a new diet.
Understand how activity level multiplies your resting calorie needs.
Plan macro splits by starting from an accurate TDEE baseline.
Track how BMR changes as you age or change body weight.
Help clients set calorie targets as a personal trainer or dietitian.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu