BMR Calculator
Your BMR is the minimum calories your body needs to survive. It's the starting point for calculating your full daily calorie needs.
Last updated: May 2026
Enables a third formula that accounts for your lean muscle mass directly.
What Is Basal Metabolic Rate?
Your Basal Metabolic Rate (BMR) represents the energy your body expends at complete rest to maintain essential physiological functions. This includes maintaining body temperature, circulating blood, breathing, and keeping every cell in your body alive.
BMR typically accounts for 60-75% of your total daily calorie burn, making it the most important factor in your overall energy equation.
Knowing your BMR is the first step. To find out how many calories you actually burn in a day, use your BMR result with our TDEE Calculator to factor in your physical activity level. Most people require 20–50% more calories than their BMR just to maintain their current weight.
Scientifically Validated BMR Formulas
Mifflin-St Jeor Default
Male: (10 × kg) + (6.25 × cm) − (5 × age) + 5
Female: (10 × kg) + (6.25 × cm) − (5 × age) − 161
The current clinical gold standard, published in The American Journal of Clinical Nutrition, 1990.
Harris-Benedict
Male: 88.362 + (13.397 × kg) + (4.799 × cm) − (5.677 × age)
Female: 447.593 + (9.247 × kg) + (3.098 × cm) − (4.330 × age)
The classic metabolic study from 1919, re-evaluated in 1984 for modern accuracy.
Katch-McArdle (requires body fat %)
BMR = 370 + (21.6 × lean mass in kg)
Utilizes Lean Body Mass; recommended for users with accurate body fat data from DEXA or skinfold tests.
BMR & Metabolic Health FAQ
Basal Metabolic Rate (BMR) is most accurate when measured in a clinical laboratory under strict conditions: after 12 hours of fasting, 8 hours of sleep, and in a temperature-controlled environment.
For most users at home, the term Resting Metabolic Rate (RMR) is technically more accurate, as it accounts for the body's energy expenditure while at rest but not under laboratory constraints. While "BMR" is the industry-standard term, we utilize the Mifflin-St Jeor equation, which clinical studies have found to be the most reliable for predicting RMR in modern populations. For athletes or those with a verified body fat percentage, the Katch-McArdle formula provides the highest precision by factoring in lean tissue.
BMR (Basal Metabolic Rate) is the number of calories your body needs to perform basic life-sustaining functions at complete rest: breathing, circulation, cell production, and organ function.
BMR is your resting calorie burn only. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor to account for movement and exercise.
The Mifflin-St Jeor equation is considered the most accurate for most people. The Katch-McArdle formula is more accurate if you know your body fat percentage, as it accounts for lean mass directly. Accuracy also depends on having a healthy body composition. You can find your target range using our Ideal Weight Calculator.
Several physiological variables determine your metabolic baseline, most notably your total lean muscle mass, as muscle tissue is significantly more metabolically active than fat even at rest. Age also plays a critical role, as the body’s basal metabolic rate naturally tends to decline by approximately one to two percent per decade after age 20 due to the gradual loss of lean tissue. Additionally, temporary factors such as hormonal fluctuations, thyroid health, and even elevated body temperature from a fever can cause your energy expenditure to spike or drop as the body works to maintain internal homeostasis.
Related Calculators
Disclaimer: Results are estimates based on population averages and established equations. Individual results may vary. Always consult a registered dietitian or healthcare professional before making significant dietary changes.