RMR Calculator - Resting Metabolic Rate

Created by Filip Derma and Łucja Zaborowska, MD, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Based on research by
Harris JA, Benedict FG. A Biometric Study of Human Basal Metabolism. The Proceedings of the National Academy of Sciences (PNAS) (1918)See 3 more sources
McMurray RG, Soares J, Caspersen CJ, McCurdy T. Examining Variations of Resting Metabolic Rate of Adults: A Public Health Perspective Medicine & Science in Sports & Exercise (MSSE) (July 2014)Livingston EH, Kohlstadt I. Simplified resting metabolic rate-predicting formulas for normal-sized and obese individuals Obesity Research (July 2005)Kinabo JL, Durnin JV. Thermic effect of food in man: effect of meal composition, and energy content. British Journal of Nutrition (July 1990)
Last updated: Nov 25, 2022

The RMR calculator is a tool that can provide you with 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. The article below provides detailed information about what RMR is, resting calories, a comparison of BMR vs. RMR, and how to use the calculator. Don't hesitate to check it!

Prefer watching over reading? Learn all you need in 90 seconds with this video we made for you:

RMR calculator

The resting metabolic rate calculator estimates the number of calories your body uses to keep it alive (in rest time). Calculations are based on the Harris-Benedict formula (see the Harris-Benedict calculator). This modification allows us to account for the calories burned during food digestion due to the so-called thermic effect of food.

Digestion increases your basal metabolic rate by 5-10%. For example, if you eat 1800 calories one day, your body will use about 90-180 of them for digesting, absorbing, and storing meal nutrients.

💡 You might also be interested in our running calorie calculator.

What is RMR?

RMR is the abbreviation of resting metabolic rate. This parameter tells how many calories your body requires 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; and
  • Sustaining the function of vital organs.

RMR does not account for calories burned to support physical activity (see calories burned calculator). Anything we do throughout the 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 (see lean body mass calculator).
  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 – regularly eating small meals will increase your RMR.
  6. Pregnancy – also can cause an increase in RMR.
  7. Crash-dieting – it decreases the RMR.

BMR vs. RMR

Besides RMR, there is also a term basal metabolic rate (BMR). This is something different than resting metabolic rate. BMR measurements are more strict than those of RMR – the BMR test requires a 24-hour rest and an overnight fast, while the RMR needs only a 15-minute relaxation period.

The BMR doesn't take into account, e.g., 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.

How many calories do I burn at rest?

We will find out 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

FAQ

How do you use RMR to lose weight?

To lose weight, try to eat slightly more than your RMR. Your RMR 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 severe diet change, and stop if you start 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 most of the CO2 produced during respiration leaves the body via the mouth. This procedure 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, so the research is somewhat limited. There may be an unknown effect, 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 and Łucja Zaborowska, MD, PhD candidate
Gender
Male
Your age
years
Your height
ft
in
Your weight
lb
Resting metabolic rate
kcal / day
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