Introduction
Your resting metabolic rate (RMR) is the number of calories your body burns each day just to stay alive. Even when you sleep, your body uses energy to breathe, pump blood, and keep your organs working. Knowing your RMR helps you understand how many calories you need to eat each day to maintain, lose, or gain weight.
This free RMR calculator uses three trusted formulas (Mifflin-St Jeor, Harris-Benedict Revised, and Cunningham) to estimate your resting metabolic rate based on your age, sex, height, and weight. It also uses your activity level to show your total daily energy expenditure (TEE), which is the full number of calories you burn when daily movement and exercise are included. Enter your details below to see your results, complete with a step-by-step breakdown of how each formula works.
How to Use Our RMR Calculator
Enter your body stats below to find your resting metabolic rate (RMR). The calculator will show how many calories your body burns at rest each day and estimate your total daily calorie needs.
Unit System: Pick Imperial or Metric. This sets your height and weight fields to pounds and feet or kilograms and centimeters. You can also change units for each field on its own.
Age: Enter your age in years. You must be between 18 and 100 years old to use this calculator.
Biological Sex: Choose Male or Female. The formulas use different numbers for each sex.
Height: Enter your height in feet and inches or in centimeters. Use the toggle above the field to switch between the two.
Weight: Enter your weight in pounds or kilograms. Use the toggle above the field to switch between the two.
Activity Level: Select how active you are on a typical week. Options range from Sedentary (little or no exercise) to Very Heavy (multiple daily training sessions). This is used to estimate your total daily calories burned.
Body Composition Input: Choose how you want to handle body fat. Pick "Use standard formulas" if you do not know your body fat percentage. Pick "I know my body fat percentage" and type it in to add the Cunningham formula, which uses your lean body mass. Pick "Estimate body fat % from BMI" to let the calculator approximate it from your BMI; this is a rough estimate built into the calculator, and a measured body fat percentage gives a better result. The African American adjustment box applies a small correction.
Calculate RMR: Press the blue Calculate button to see your results. You will get your RMR from up to three proven formulas, a bar chart comparison, a step-by-step math breakdown, a calorie table for every activity level, and a comparison to population averages.7
What Is Resting Metabolic Rate (RMR)?
Your resting metabolic rate is the number of calories your body burns each day just to stay alive. Even when you are sleeping or sitting still, your body uses energy to breathe, pump blood, and keep your organs working.8 RMR is the largest share of the calories you burn in a day.
How This RMR Calculator Works
This calculator uses your age, sex, height, and weight to estimate your RMR. It gives you results from up to three trusted formulas:
- Mifflin-St Jeor (1990): Published in 1990 from measurements in 498 healthy adults aged 19 to 78, and the default here.2 It uses your total body weight, height, age, and sex, with the unrounded coefficients from the original paper.
- Harris-Benedict Revised (1984): An older formula that is still widely used. Harris and Benedict first published it in 1918.3 The coefficients here are Roza and Shizgal's 1984 re-fit,4 as printed in a 2021 systematic review of prediction equations.5 It works the same way as Mifflin-St Jeor but uses different numbers in the equation.
- Cunningham / Katch-McArdle (1991): This formula uses your lean body mass instead of total weight. The equation, 370 + 21.6 × lean mass, is Cunningham's 1991 general prediction equation, which is also the one usually labelled Katch-McArdle.6 Lean mass is your weight times one minus your body fat fraction. It appears when you enter your body fat percentage or choose to estimate it from BMI. Most existing formulas underestimate the resting calorie burn of athletes, because athletes carry more lean mass.9 In a study of recreational athletes, an older version of Cunningham's equation, 500 + 22 × lean mass, came within 10% of measured RMR more often than any other formula tested.9 The 1991 version used here gives lower results than that older one.
RMR vs. BMR
RMR and basal metabolic rate (BMR) are very similar. BMR is measured under strict lab conditions: awake and lying down, after 10 to 12 hours without food and 8 hours of physical rest, in a room that is neither warm nor cool enough to make the body heat or cool itself.8 RMR is measured under slightly less strict conditions.7 In everyday use, the two terms mean nearly the same thing.
Total Daily Energy Expenditure (TEE)
Your RMR only covers the calories you burn at rest. To find out how many total calories you burn each day, the calculator multiplies your RMR by an activity factor.8 A more active lifestyle means a higher multiplier and more calories burned. This total number is called your Total Energy Expenditure, or TEE. Knowing your TEE helps you plan how much to eat whether your goal is to lose weight, gain muscle, or maintain your current weight.
Why RMR Matters
Knowing your RMR gives you a starting point for building a nutrition plan. If you eat fewer calories than your TEE, you will likely lose weight over time. If you eat more, you will likely gain weight. Your RMR can also change based on factors like age, muscle mass, and hormones. Regular exercise and strength training can help raise your RMR by building more lean muscle.