BMR Calculator: How To Calculate Your Basal Metabolic Rate

A Basal Metabolic Rate (BMR) calculator determines the minimum calories your body burns to survive. It considers certain factors such as age, height, weight, sex, and fat percentage (in some equations). Based on the calories from your BMR, you can then determine how many calories you need to lose, gain or maintain your weight.

To start, please answer the following question:

Do you know your body fat percentage?

What is BMR?

The BMR is how many calories you need to live. They are the minimum calories your body needs for your organs to perform their most basic tasks (heart beating, nutrient processing, breathing, cell production, temperature regulation, and circulation). 

In other words, the BMR is the calories you need to be lying in a bed and simply exist. 

Your BMR represents approximately 60 to 70% of the total calories you eat. The remaining calories come from your food’s thermogenesis (calories burned to process foods) and your activity levels. 

How The BMR Calculator Works

Our BMR calculator uses the Mifflin St. Jeor equation (if you don’t know your fat percentage) or the Cunningham equation (if you have your fat percentage). While you can do these calculations on your own, the formulas might be hard to understand or calculate. While the BMR calculator above helps you determine your BMR automatically, below are the equations used. 

Mifflin St. Jeor Equation

If you don’t know your bodyfat percentage, then the Mifflin St. Jeor Equation is used. The formula is: 

  • Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
  • Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161

Cunningham Equation

If you know your bodyfat percentage, then the Cunningham Equation is used.  The formula is:

BMR = 500+22*{kg of free fat mass (FFM)

BMR Variables 

Certain variables can affect the result of your BMR. The most common ones are the ones that you input into the formulas above: 

  • Age
  • Weight
  • Height
  • Sex
  • Fat mass 
  • Muscle mass

Other variables can affect the BMR but are harder to contemplate in the equation, such as hormonal changes, ethnicity, weight loss history, pregnancy, supplements, and genetic factors. 

What To Do With Your BMR Results

Once you have your BMR, you can calculate your Total Daily Energy Expenditure (TDEE). This estimates how many calories you need per day to maintain your weight. In other words, these are your maintenance calories

Not only does it take into account your BMR, but it also adds to the thermogenic effect of food (calories burned by processing food) and your activity levels (exercise and daily movement). 

When you have your maintenance calories, you can figure out how many you need to lose or gain weight. 

If you wish you lose weight, you need to be in a caloric deficit. This means consuming fewer calories than your body needs. You can subtract anywhere from 200 to 500 calories from your maintenance calories or subtract 5 to 20% of your calories. 

For example, if you have a maintenance caloric intake of 2,000 calories, you can subtract 500 calories to be in a deficit. You can also subtract 20%, which would mean subtracting 400 calories.

Either option you choose, make sure never to go below your BMR. Going below your BMR can make it less efficient in weight loss. 

On the other hand, if you wish to gain weight, you need to be in a caloric surplus. This means eating more calories than your body needs. You can increase 200 to 500 calories or do it based on a percentage. You can add 5 to 20% extra calories to your maintenance calories. 

For example, based on the maintenance calories of 2,000 calories, if you want to be in a caloric surplus, you would need to consume 2,200 calories. Or you can add up to 20% extra calories, giving you a slightly higher caloric surplus of 2,400 calories. 

What Is A Healthy BMR? 

There is no such thing as a healthy or good BMR. Everyone has their own BMR based on their age, weight, height, body composition, and hormonal processes. So, not everyone is going to have the same BMR. 

There are some factors that can modify your BMR like exercise, medications, and stress levels. 

When you have a low BMR, it means you need to eat fewer calories to support your body. It also means that you might need a lower caloric intake to lose weight, which might make it more difficult to achieve. If this is the case for you, check out our articles on how to get used to eating less and how to eat 1200 calories and feel full.

Related Articles: 

BMR vs. RMR: What Are The Differences?

While a lot of people use Basal metabolic rate (BMR) and resting metabolic rate (RMR) interchangeably, they are two different things. 

  • BMR is the number of calories you need for your body to survive and perform necessary functions.
  • RMR is the calories your body needs at rest. This means your BMR plus some basic daily activities like eating, short walks, drinking, sweating, and going to the bathroom. 

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