RMR Calculator - Resting Metabolic Rate

By Filip Derma
Last updated: Feb 10, 2021

RMR calculator is a tool which can provide you an answer to the question "how many calories do I burn at rest?" Insert a few basic parameters and find your resting metabolic rate value. In the article below, you will find detailed information about what is RMR, resting calories, a comparison BMR vs RMR, and how to use the calculator. Don't hesitate to check it!

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 allowes 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).

How many calories do I burn at rest?

We will find how to use the calculator by investigating the example below. We assumed some parameters for our average person.

The RMR calculator step by step:

  1. Choose the gender: gender = male
  2. Enter the age: age = 30 years
  3. Fill in the height of the person: height = 180 cm
  4. Insert weight: weight = 80 kg
  5. The resting metabolic rate of this person is: RMR = 2050 calories / day


How do you use RMR to lose weight?

To lose weight, try to eat slightly more than your RMR. This is the minimum calories you need per day to survive, so your body will get the rest from its stored energy sources, e.g. fat. However please consult your doctor before beginning any serious diet change, and stop if you begin to feel any pain.

Is RMR testing accurate?

The most accurate way to find your RMR is to visit a licensed facility. The test involves you breathing into a small device for roughly 10 minutes, as the majority of the CO2 produced during respiration leaves the body via the mouth. This is, however, expensive, and using an online calculator is a free alternative, with an accuracy of +/- 300 calories.

Do long fasts slow your RMR?

The current research suggests that fasting does not affect RMR in a significant way. However, this is a new field of interest, and so the research is rather limited, so there may be a yet unknown affect, or the research could be wrong. Please consult your doctor before going on any serious fasts and consider stopping if you begin to exhibit any unwanted symptoms.

Does a keto diet affect your RMR?

A recent study found that there was no significant statistical change in RMR in obese patients using a very low-calorie ketogenic diet to lose a large amount of weight (~20 kg). However, ketogenic diets are a relatively new trend, so the current studies are limited and may not be accurate.

Filip Derma
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