RMR Calculator
A 30-year-old man weighing 70 kg at 175 cm has an estimated RMR of 1,696 calories a day with this formula. This RMR calculator estimates resting metabolic rate from sex, age, weight, and height using the Revised Harris-Benedict equation. Resting metabolic rate is the energy your body uses to keep basic functions running while you are awake, resting, and not digesting a large meal or exercising. That makes it a useful baseline for nutrition planning, coaching conversations, and general calorie awareness, even though it is not the same as total daily calorie needs. Use this RMR calculator when you want a quick estimate before adding activity, exercise, or goal-based calorie adjustments. The result can help you compare scenarios such as recent weight changes, aging over time, or the difference between two body sizes. Because metabolism is affected by body composition, hormones, health status, and measurement conditions, the output should be treated as a planning estimate rather than a direct measurement of your metabolism.
Quick answer
RMR estimates how many calories your body uses in a normal resting state over 24 hours, before steps, workouts, or job activity are added.
What this tells you
- •RMR estimates how many calories your body uses in a normal resting state over 24 hours, before steps, workouts, or job activity are added.
- •This page uses the Revised Harris-Benedict equation, which gives different coefficients for male and female inputs and then adjusts the estimate for weight, height, and age.
- •Weight and height usually push the estimate up, while older age lowers it slightly in the equation.
- •BMR is a stricter laboratory-style concept, so many people will see RMR described as a practical estimate that often sits a bit above true BMR.
- •The result is most useful as a starting point for calorie planning, not as proof of a medical condition or an exact measure of daily energy burn.
How to Use
- 11. Select the sex input that matches the formula option you want to use. This tool applies one equation for male inputs and another for female inputs.
- 22. Enter age in years using your current age, not the age you were during a past diet, sports season, or medical visit.
- 33. Enter current body weight in kilograms. If your scale shows pounds, convert to kilograms first so the formula stays accurate.
- 44. Enter height in centimeters. Shoes, posture, and rounding can change the estimate a little, so use a realistic measured height rather than a guess.
- 55. Calculate to see your estimated resting calories per day. If you are planning meals, compare this number with an activity-adjusted total instead of using RMR alone.
How It Works
Formula
Male: RMR = 88.362 + 13.397W + 4.799H - 5.677A
Female: RMR = 447.593 + 9.247W + 3.098H - 4.330AThis tool uses the Revised Harris-Benedict equation exactly as implemented in the site formula file. In the expression, W is weight in kilograms, H is height in centimeters, and A is age in years. For male inputs, the calculator starts with 88.362, adds 13.397 times weight, adds 4.799 times height, and subtracts 5.677 times age. For female inputs, it starts with 447.593, adds 9.247 times weight, adds 3.098 times height, and subtracts 4.330 times age. After the formula is evaluated, the tool rounds the final value to the nearest whole calorie per day. The equation estimates resting energy expenditure under ordinary resting conditions, which is why the result should not be treated as the same thing as calories burned across a full day. To move from RMR to a fuller daily calorie target, you would usually account for movement, structured exercise, digestion, and any guidance from a clinician or dietitian.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Estimated RMR for a 30-year-old man
Using the male formula, 88.362 + (13.397 × 70) + (4.799 × 175) - (5.677 × 30) = 1,696.107. The tool rounds that to 1,696 kcal/day. This is a resting estimate only, so daily calorie needs would usually be higher after activity and digestion are included.
Estimated RMR for a 32-year-old woman
Using the female formula, 447.593 + (9.247 × 68) + (3.098 × 165) - (4.330 × 32) = 1,448.989. The calculator rounds the result to 1,449 kcal/day. This example shows how a moderate change in body size and a different coefficient set can shift the estimate even when two adults are fairly close in age.
Estimated RMR for a 45-year-old man with a larger frame
Using the male formula, 88.362 + (13.397 × 90) + (4.799 × 180) - (5.677 × 45) = 1,902.077. Rounded to the nearest whole calorie, the estimate is 1,902 kcal/day. Compared with the first example, the higher weight and taller height raise resting needs even though older age pulls the result down slightly.
Estimated RMR for a 27-year-old woman with a smaller body size
Using the female formula, 447.593 + (9.247 × 55) + (3.098 × 160) - (4.330 × 27) = 1,335.258. The displayed value becomes 1,335 kcal/day after rounding. This is a good reminder that RMR changes with body size, so copying another person's number is rarely useful.
Estimated RMR for a 60-year-old man
Using the male formula, 88.362 + (13.397 × 82) + (4.799 × 172) - (5.677 × 60) = 1,672.448. The calculator rounds this to 1,672 kcal/day. Even with a solid body weight, the age term lowers the estimate compared with a younger adult of similar size.
Estimated RMR for a 40-year-old woman
Using the female formula, 447.593 + (9.247 × 78) + (3.098 × 170) - (4.330 × 40) = 1,522.289. Rounded to the nearest calorie, the estimate is 1,522 kcal/day. This kind of example is useful when you want a baseline before applying an activity multiplier or comparing maintenance estimates from another calorie calculator.
Common mistakes
- Treating RMR as the same as total daily calorie needs. RMR is only the resting baseline, so it does not include workouts, walking, job activity, or the thermic effect of food.
- Using old body measurements after recent weight change. A number based on last year's weight or a guessed height can shift the result enough to matter.
- Entering pounds as kilograms or feet as centimeters. Unit mistakes can distort the estimate far more than the normal error range of the equation.
- Comparing two results without noticing the age effect. Even when height and weight are similar, the age term changes the final estimate.
- Assuming the estimate reflects muscle mass, thyroid status, medication effects, or clinical conditions. The formula cannot see those factors directly.
Limitations
This equation uses population averages and sex-specific coefficients, then rounds the answer to the nearest whole calorie. It does not directly measure metabolism, and it cannot account for lean mass, body fat distribution, thyroid disease, fever, recent hard training, recovery status, menopause, pregnancy, medications, adaptive dieting effects, or results from indirect calorimetry. It is also meant for adults, so it is not the right tool for children or for clinical nutrition decisions that need measured energy expenditure.
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