BMR / RMR Calculator
Free Bmr rmr Calculator for overall fitness. Enter your stats to get performance metrics and improvement targets. Includes formulas and worked examples.
Reviewed by Sher, Sports Science & Nutrition Specialist
Formula
BMR = 10W + 6.25H - 5A + S
Mifflin-St Jeor equation where W = weight in kg, H = height in cm, A = age in years, S = +5 for males or -161 for females. TDEE = BMR multiplied by activity factor (1.2 to 1.9).
Worked Examples
Example 1: Male Athlete BMR Calculation
Problem:Calculate BMR for a 28-year-old male, 82 kg, 180 cm, 14% body fat, moderately active (trains 4x/week).
Solution:Mifflin-St Jeor: BMR = 10(82) + 6.25(180) - 5(28) + 5 = 820 + 1125 - 140 + 5 = 1,810 kcal\nHarris-Benedict: BMR = 88.362 + 13.397(82) + 4.799(180) - 5.677(28) = 1,907 kcal\nKatch-McArdle: LBM = 82 x 0.86 = 70.52 kg, BMR = 370 + 21.6(70.52) = 1,893 kcal\nTDEE (x1.55) = 1,810 x 1.55 = 2,806 kcal
Result:BMR: 1,810 kcal (Mifflin) | RMR: 1,991 kcal | TDEE: 2,806 kcal
Example 2: Female Weight Loss Planning
Problem:A 35-year-old female, 65 kg, 163 cm, lightly active. Calculate BMR and target calories for moderate weight loss.
Solution:Mifflin-St Jeor: BMR = 10(65) + 6.25(163) - 5(35) - 161 = 650 + 1019 - 175 - 161 = 1,333 kcal\nRMR = 1,333 x 1.1 = 1,466 kcal\nTDEE = 1,333 x 1.375 = 1,833 kcal\nModerate deficit (500 kcal): 1,833 - 500 = 1,333 kcal\nExpected loss: ~0.45 kg/week (1 lb/week)
Result:BMR: 1,333 kcal | TDEE: 1,833 kcal | Weight loss target: 1,333 kcal/day
Frequently Asked Questions
What is the difference between BMR and RMR?
Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) both measure the calories your body burns at rest, but they differ in measurement conditions. BMR is measured under strict laboratory conditions after 12 hours of fasting, 8 hours of sleep, and in a thermoneutral environment. RMR is measured under less restrictive conditions and typically runs 10 to 15 percent higher than BMR. In practice, RMR is more commonly measured because the strict BMR testing protocol is difficult to implement. For most practical purposes, the terms are used interchangeably, though RMR more accurately reflects the calories you actually burn during rest in everyday life.
Which BMR equation is the most accurate for estimating metabolic rate?
The Mifflin-St Jeor equation is considered the most accurate for the general population and is recommended by the American Dietetic Association. Studies show it predicts BMR within 10 percent accuracy for about 80 percent of people, compared to 70 percent for the Harris-Benedict equation. However, the Katch-McArdle and Cunningham equations are superior for athletes and lean individuals because they account for body composition. Since muscle tissue is more metabolically active than fat tissue, two people of the same weight but different body fat percentages will have significantly different metabolic rates. Using lean body mass-based equations eliminates this confounding variable.
How does age affect BMR and why does metabolism slow down?
BMR typically decreases by approximately 1 to 2 percent per decade after age 20, primarily due to loss of lean muscle mass (sarcopenia) and changes in hormonal profiles. Between ages 30 and 70, most people lose roughly 3 to 8 percent of muscle mass per decade if they do not engage in resistance training. This muscle loss directly reduces metabolic rate because muscle tissue consumes significantly more calories at rest than fat tissue. Hormonal changes including decreasing testosterone, growth hormone, and thyroid function further contribute to metabolic decline. However, this decline is not inevitable. Regular resistance training can preserve or even increase muscle mass, maintaining a higher metabolic rate well into older age.
Why do men typically have higher BMR than women?
Men generally have higher BMR than women primarily because of differences in body composition. On average, men carry 10 to 15 percent more lean muscle mass and 6 to 10 percent less body fat than women of similar height and weight. Since muscle tissue is metabolically active (burning roughly 6 calories per pound per day at rest versus 2 calories per pound for fat), more muscle means higher resting energy expenditure. Hormonal differences also play a role, with higher testosterone levels promoting greater muscle protein synthesis and maintenance. Additionally, men tend to have larger organ mass (particularly heart and liver), which are among the most metabolically active tissues. These factors combined explain the roughly 5 to 10 percent BMR difference.
References
Reviewed by Sher, Sports Science & Nutrition Specialist · Editorial policy