RMR Calculator – Resting Metabolic Rate

RMR Calculator – Resting Metabolic Rate

RMR calculator

The resting metabolic rate calculator estimates the amount of calories used by your organism to keep it alive (in rest time). Calculations base on a modified Harris-Benedict formula. This modification allows to sum calories that are burned during food digestion. Digestion increases your basal metabolic rate by 5-10%. For example, if you eat 1800 calories one day, about 90-180 of them will be used for digesting, absorbing, and storing meal nutrients.

What is RMR?

RMR is the abbreviation of resting metabolic rate. This parameter tells how many calories are required by your body to perform the most basic functions (to keep itself alive) while resting. These essential functions are e.g.:

  • breathing
  • heart beating
  • circulating blood
  • basic brain functions
  • food digestion
  • sustaining the function of vital organs

RMR does not account for calories burned to support physical activity. Anything that we do through a day requires energy (calories) to be burned in addition to those used to support resting metabolic rate.

What can affect your resting metabolic rate?

A few factors can significantly impact your RMR:

  1. Muscle – more muscle will increase RMR
  2. Age – RMR decreases with age
  3. Genetics – can influence your natural level of RMR
  4. Climate – living in a cold environment can increase your RMR
  5. Meals – eating small meals regularly will increase your RMR
  6. Pregnancy – also can cause the increase in RMR
  7. Crash-dieting – it decreases the RMR


Besides RMR, there is also a term basal metabolic rate (BMR). This is something different than resting metabolic rate. It doesn’t take into account calories utilized for food digestion. That’s the reason why RMR is considered to be more reliable in the estimation of resting calories. Your body is usually digesting some amount of food at every moment of time. To perform a basal metabolic rate measurement (in the laboratory environment), you need to fast at least 12 hours (where for RMR it is not required at all).