Unit System:
years
Calculation results
RMR: Calories per day
Resting Metabolic Rate Calculator
What Resting Metabolic Rate Tells You
Resting metabolic rate is the energy your body burns just keeping your heart, lungs, brain, and organs running through an ordinary day. It typically makes up 60 to 70 percent of everything you expend. Knowing this number turns calorie planning from guesswork into basic arithmetic. Dietitians, weight loss clinics, and self coached lifters all start their nutrition math here.
RMR sits slightly above BMR because it includes low effort states like sitting quietly or finishing a meal. Testing conditions, food, and time of day explain the gap. Most meal plans treat the two values as interchangeable.
The Mifflin-St Jeor Formula Behind the Estimate
The calculator applies the Mifflin-St Jeor equation, widely regarded as the most reliable predictive formula available. Men compute 10 x weight in kg plus 6.25 x height in cm minus 5 x age plus 5, while women run the same math and subtract 161 instead.
Example: a 30 year old man weighing 70 kg at 175 cm tall computes 700 plus 1093.75 minus 150 plus 5. That lands at about 1648 calories per day. A woman with identical stats would get roughly 1488. The 166 calorie gap between the genders comes from the constants.
How to Use This Calculator
Select Imperial or Metric, then enter Age, Gender, Height, and Weight and press Calculate. Imperial mode takes feet and pounds; Metric takes centimeters and kilograms. Log the measurements you carry today, not the goal weight you want, since the formula only describes your current body. Very muscular and older adults can drift from the estimate.
Expect a margin of error near plus or minus 10 percent. Treat the output as your sedentary baseline, then add exercise on top instead of rounding the figure up. Recalculate after every 3 to 5 kg of weight change.
Frequently Asked Questions
How accurate is the Mifflin-St Jeor equation?
Studies put it within about 10 percent of measured values for most adults. It generally beats older equations like Harris-Benedict, especially at higher body weights.
Is RMR the same as BMR?
No, though they are close. RMR usually reads 50 to 100 calories higher because it quietly allows resting states that a strict BMR measurement excludes.
Why does RMR drop with age?
Muscle mass declines roughly 3 to 8 percent per decade after age 30, and muscle is metabolically expensive tissue. Less lean mass means fewer resting calories.
Should I ever eat below my RMR?
Deficits below your RMR risk muscle loss and rebound hunger. Most plans keep intake at least 1200 calories for women or 1500 for men unless a doctor supervises.
How often should I recalculate my RMR?
Recheck after every 3 to 5 kg of weight change, a big shift in training, or each birthday past 40. Composition changes move the math quickly.