RMR Calculator
Calculate your Resting Metabolic Rate using scientifically validated formulas
Sex affects the formula constants used in RMR calculation
Age in years (1–120). Formulas are most accurate for ages 18–65.
Required for Cunningham and Katch-McArdle formulas. Unlocks lean-mass-based calculations.
Mifflin-St Jeor is the gold standard for most people. Cunningham is best for athletes.
Select your typical weekly exercise frequency to calculate TDEE
Used to calculate your recommended daily calorie intake
Enter Your Body Measurements
Input your age, gender, height, and weight to calculate your Resting Metabolic Rate using multiple formulas.
How to Use the RMR Calculator
Enter Your Basic Stats
Select your unit system (US Imperial or Metric), then enter your biological sex, age, height, and weight. These four inputs are required for every RMR formula. For the most accurate results, weigh yourself first thing in the morning without clothing and measure your height without shoes.
Choose a Formula and Add Optional Body Fat
Select Mifflin-St Jeor for the most accurate general-population result. If you are an athlete or know your body fat percentage, enter it and select the Cunningham or Katch-McArdle formula for lean-mass-based calculation. The calculator will display all formulas side-by-side in the results for comparison.
Set Your Activity Level and Weight Goal
Select your typical weekly exercise level from the five options (Sedentary to Extra Active). This multiplies your RMR to give your TDEE — total daily calorie burn. Then choose your weight goal (loss, maintenance, or gain) to see your recommended daily calorie intake.
Analyze Your Results and Plan Your Diet
Review your RMR, TDEE, and calorie goal. Check the Formula Comparison bars to see how the three formulas agree. Use the Activity Level table to see how your TDEE changes with different exercise frequencies. Adjust your actual food intake based on results over 2–4 weeks and recalculate as your weight changes.
Frequently Asked Questions
What is RMR and how is it different from BMR?
RMR (Resting Metabolic Rate) is the number of calories your body burns each day to maintain basic functions — breathing, circulation, organ function — while at rest. BMR (Basal Metabolic Rate) measures the same thing but under much stricter laboratory conditions: after a full night of sleep, a 12-hour fast, and 30 minutes of complete stillness in a temperature-controlled room. RMR is measured after just 15 to 20 minutes of rest, making it more practical and slightly higher than BMR — typically by 10 to 20 percent. For everyday nutrition planning purposes, RMR is the more useful number because it better reflects real-world resting conditions. Most online tools that label themselves BMR calculators actually calculate RMR using the same formulas, so the distinction is largely semantic in practice.
Which RMR formula is most accurate for me?
The Mifflin-St Jeor equation (1990) is the most accurate formula for the general population and is recommended by the Academy of Nutrition and Dietetics. It predicts RMR within 10% of indirect calorimetry for most non-obese individuals, and also performs reasonably well for obese individuals. If you are an athlete, bodybuilder, or lean person with known body fat percentage, the Cunningham equation is more accurate because it uses lean body mass instead of total weight — muscle mass is the primary driver of metabolic rate. The revised Harris-Benedict equation (1984) is a reliable alternative used widely in clinical settings. If you have body fat percentage data, try both Mifflin-St Jeor and Cunningham and use the result that aligns better with your real-world calorie needs.
How can I use my RMR to lose weight?
Your RMR combined with your activity level gives your TDEE — total daily energy expenditure. To lose fat, eat fewer calories than your TDEE. A deficit of 250 to 500 calories per day creates safe, sustainable fat loss of 0.5 to 1 pound per week. A 1,000-calorie deficit produces approximately 2 pounds per week but increases the risk of muscle loss and metabolic slowdown. Never eat below your RMR for extended periods, as this deprives your body of energy for vital organ function and triggers metabolic adaptation that makes further weight loss harder. Women should not eat below 1,200 kcal/day and men should not go below 1,500 kcal/day without medical supervision. Combine your calorie target with adequate protein (0.7 to 1 gram per pound of body weight) and resistance training to preserve muscle.
What factors affect my resting metabolic rate?
The most important factors are lean muscle mass (muscle burns more calories at rest than fat), age (metabolic rate declines about 2% per decade after age 20 due to muscle loss), and gender (men typically have higher RMRs due to greater muscle mass). Thyroid function is another major factor — an underactive thyroid can significantly suppress metabolic rate. Genetics play a role, accounting for 40 to 70 percent of the variation in RMR between individuals. Other contributors include sleep quality (poor sleep reduces metabolic rate), the severity of past dieting history (very low calorie diets cause metabolic adaptation), body temperature (fever increases it), and certain medications. Factors like climate, altitude, and chronic stress can also cause modest changes in RMR.
Can I increase my resting metabolic rate?
Yes, several evidence-based strategies can increase your RMR over time. Resistance training and muscle building is the most effective long-term strategy — each kilogram of muscle added burns approximately 13 extra calories at rest per day. High-intensity interval training (HIIT) creates a temporary post-exercise metabolic elevation called EPOC (excess post-exercise oxygen consumption). Eating adequate protein increases the Thermic Effect of Food (TEF) since protein has a higher thermal cost to digest than carbohydrates or fat. Staying well hydrated supports cellular metabolic processes. Getting 7 to 9 hours of quality sleep per night is critical because sleep deprivation measurably reduces metabolic rate and increases fat storage hormones. Avoiding prolonged severe caloric restriction prevents metabolic adaptation, which can lower RMR by 15 to 30 percent.
How accurate are online RMR calculators compared to lab testing?
Online RMR calculators, including this one, typically have an accuracy range of plus or minus 200 to 300 kilocalories compared to laboratory-measured RMR using indirect calorimetry — the gold standard test. This means your actual metabolic rate could be up to 15 to 20 percent higher or lower than the calculator estimate. The variation exists because formulas are derived from population averages and cannot account for individual differences in genetics, hormonal status, gut microbiome, medication effects, and metabolic history. Studies show that the Mifflin-St Jeor formula predicts RMR within 10% of indirect calorimetry for approximately 80% of individuals. The best approach is to use the calculator result as a starting estimate, then track your actual weight and food intake for 2 to 4 weeks and adjust your calorie target based on real-world results.