What Is BMR and How Do You Calculate It?

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What Is BMR and How Do You Calculate It?

BMR stands for Basal metabolic rate and is the average amount of calories your body needs to keep your organs alive each day.

That said, it's an estimate of the absolute minimum number of calories your body needs to maintain basic functions like breathing, hormone production, cell repair and nothing else.

You can accurately estimate your BMR by entering your gender, weight, height, and age into a BMR equation, or by entering the same information in the box Legion BMR calculatorwho does all the math for you.

Once you know your BMR, you can use it to create a nutrition plan to help you lose, gain, or maintain your weight.

Read on to learn how!

What is BMR?

Your basal metabolic rate (BMR) is a hypothetical estimate of the amount of energy your body burns to maintain important physiological functions, but nothing more.

This includes processes like pumping blood, breathing, regenerating cells and so on.

The reason your BMR a. is hypothetical It is estimated that this will change based on a variety of factors including your diet, environmental conditions, activity level, stress, sleep levels, and other factors. Hence, it is impossible to determine exactly what your BMR is at any given point in time.

So scientists use mathematical models to predict what your BMR is because they can't measure it directly.

Here's a great way to think about it:

Imagine it is 2091 and to protect ourselves from COVID-91 we decided to upload our consciousness to the cloud and live in an artificial amnion in a state of suspended animation, taking food and mental stimulation from ours technocratic overlords (she knows like this).

Your BMR is roughly the number of calories it takes to keep you alive in these circumstances.

There are many formulas for estimating BMR, but which one you choose will largely depend on your personal preference and convenience (you will learn the best in a moment).

You may have heard of a similar, but slightly different, measurement than yours. is known Resting metabolic rate (RMR). This is the actual number of calories your body burns at rest, which can be influenced by factors such as previous activity or food consumption.

In other words, your BMR is the hypothetical number of calories your organs need each day to stay alive, while your RMR is the actual number of calories you would burn per day if you were completely still without to eat or exercise beforehand.

Thus, your RMR is slightly higher than your BMR, although the absolute differences are tiny and you can use both numbers more or less interchangeably for weight loss purposes.

How does calculating your BMR help you lose weight?

Whether you gain weight or lose weight is determined by Energy balance– the relationship between the energy you put into your body and the energy it uses up.

In other words, Calories in versus calories out.

While many people think exercise is the most effective way to burn calories (and it is helps pretty much!), your BMR usually makes up the bulk of the calories you burn every day.

For example, I'm 36 years old, 6-1, and 195 pounds, and my BMR is around 1,900 calories a day. On days that I exercise, I usually lift weights for about 45 to 60 minutes and do about 30 to 40 minutes of cardio, burning an additional ~ 500 to 800 calories on those days (depending on the Volume and intensity the workouts).

In other words, my BMR burns two to four times more calories a day than my exercise routine, even on the days when I don't exercise without lifting a finger. Hence, your BMR plays a key role in helping you lose weight.


Burning calories is only one side of the energy balance coin. In order to lose, gain or maintain your weight, you also need to control how many calories you are consuming.

Knowing about your BMR helps with this too.

Once you know your BMR, there are a few other formulas you can use to estimate how many total calories you are burning every day Total daily energy consumption (TDEE).

This number includes your BMR and the calories you burn from exercising, non-exercising activity, and exercising thermal effect of food (How many calories do you burn while digesting your meals).

Basically, your BMR is a component of your TDEE that is a much more useful number when it comes to controlling your body weight.

Once you know your TDEE, there are three things you can do to make effective food choices:

  • If you eat more than this number of calories each day, you will gain weight.
  • If you eat less every day, you will lose weight.
  • If you eat this much on a regular basis, you will maintain your weight.

Now, if you shake your head and think I'm drinking decades-old Kool-Aid, let me ask you a few questions.

Why does every single one have controlled weight loss? study carried out over the past 100 years. . . including countless meta-analyzes and systematic reviews. . . concluded that meaningful weight loss requires that energy expenditure exceed energy intake?

Why did bodybuilders go just as far back? . . from Sandow to Reeves and all the way up. . . I have used this knowledge to systematically and routinely reduce and increase Body fat levels?

And why do new brands of “calorie denial” come and go every year that are not accepted in the weight loss literature?

The reality is that a century of metabolism research has proven beyond a doubt that the energy balance, which works on the first law of thermodynamics, is the fundamental mechanism that regulates fat storage and reduction.

Once you accept this premise, the science of weight loss becomes brutally easy (though not necessarily easy, as with most things in life).

What's the Best BMR Formula?

The most accurate way to calculate your BMR is to go to a lab and contact one Metabolic cart.

Of course, this is also expensive and inconvenient.

Fortunately, it isn't necessary either, as there are math equations that can predict the results of any of these machines with decent accuracy.

There are many BMR formulas to choose from, but which one you choose depends mainly on your personal preference and convenience.

Personally, I use and recommend the Mifflin-St Jeor variant, which looks like this:

BMR = (9.99 x weight (kg)) + (6.25 x height (cm)) – (4.92 x age (years)) +/- (s), where "s" +5 for men and -161 is for women.

To make it easier we can break it down into male and female versions:

Male BMR = (9.99 x weight (kg)) + (6.25 x height (cm)) – (4.92 x age (years)) + 5

Female BMR = (9.99 x weight (kg)) + (6.25 x height (cm)) – (4.92 x age (years)) – 161

The reason I can recommend the Mifflin-St Jeor to others BMR formulas like Harris-Benedict or Katch-McArdle, it gives very accurate results on par with these equations, but doesn't require a lot of math or yours Body fat percentage.

A catch with the Mifflin-St Jeor equation is that it assumes a relatively normal body composition (normal muscles and 10 to 20% body fat for men and 20 to 30% for women).

Thus, the equation can overestimate the BMR of people with above average muscle mass (especially if they also have below average body fat levels) and the BMR of people in the opposite boat.

So why not use a BMR equation that includes lean body mass, such as the Katch-McArdle equation?

I did and recommended this before, but I stopped for two reasons:

  • Most people find it difficult to accurately estimate their body fat percentage, and relatively small mistakes can negate potential benefits of the equation. That is, if the equation is 5% more accurate, but your estimate of body fat percentage is 20% (relative) different, then it is a wash.
  • The Mifflin-St Jeor equation is simpler and provides estimates that are almost identical to the Katch-McArdle equation for most people.

The first point is self-explanatory: Many people think they are significantly slimmer than they are, which, using the Katch-McArdle equation, leads to an overestimated BMR. The second point, however, requires a little more explanation.

Although muscles burn more calories than body fat, the differences are not important in practice.

research shows that a pound of muscle burns about 6 calories a day (not 50 as many fitness gurus claim) and fat burns about 2 calories a day. That's a triple relative difference, but a trivial absolute difference that has little impact on your BMR.

For example, I have about 40 to 50 pounds more muscle than most men my size (6-1, 195 pounds, ~ 10% body fat, and 36 years old), and the Mifflin-St Jeor equation sticks to my BMR 1,872 calories per day.

The Katch-McArdle equation, which takes into account my extra muscle mass and low body fat percentage, estimates my BMR to be 2,089 calories per day – about 200 more calories. In the scheme of things, this is too little to matter.

And what about the Harris-Benedict equation?

This is also a workable formula that produced Results similar to the others but most researchers Consider the Mifflin-St Jeor, to be a little more precise. There's also the revised Harris-Benedict equation, which is believed to be a bit more accurate than the original (but again, not quite as accurate as the Mifflin-St Jeor equation).

Finally, I want to share with you an equation that is handy because of its simplicity: the Lyle McDonald equation for resting metabolic rate (RMR). Here it is:

Male RMR: 11 times body weight in pounds

RMR for women: 10 x body weight in pounds

Yes it is, regardless of your body composition.

As you now know, RMR is slightly different from BMR, but for our purposes here they are basically interchangeable.

My general recommendation is to use the Mifflin-St Jeor equation if you have a calculator that does the heavy lifting for you (like the Legion BMR calculator) or you want to be as precise as possible, and the Lyle McDonald equation if you want a quick and dirty solution that is almost as accurate in practice.

The right way to start thinking about BMR formulas

No BMR formula is 100% accurate for all people under all circumstances. Your lifestyle, genetics, diet, and daily habits make your actual BMR a small and moving target that formulas are unlikely to hit. Heck, even the fancy devices for measuring the BMR are not 100% accurate.

Fortunately, BMR formulas They don't have to be precise to serve their intended purpose. You just have to be good enough that you know where to start. Then you can increase or decrease your calorie intake depending on how your body is actually responding to your diet.

For example, if you cut and a TDEE equation (which includes the BMR calculation) says you should be eating 2,500 calories a day to lose weight and you don't lose weight, you need to eat less regardless of the math says.

Likewise if you Lean bulking, and one formula says that you should be eating 3,000 calories a day to gain weight, but you are not gaining weight, then you need to eat more.

The bottom line is that everything BMR formulas are estimates of your actual BMR, not precise measurements. Use them to set a starting point for your caloric intake, then adjust it up or down depending on your body's response.

This is an important point for driving home as many people agonize over whether or not they hit their BMR “perfectly”. Don't make this mistake. Pick a BMR formula you like, fill in your numbers, create a meal plan, and get to work. Then you can adjust up or down depending on the rate of progress.

How To Use A BMR Calculator For Weight Loss

This process consists of just three simple steps:

  1. Estimate your BMR with the Legion BMR calculator.
  2. Use your BMR to estimate your TDEE.
  3. Use your TDEE to create and follow a nutrition plan to help you lose, gain, or maintain weight.

Normally you'd have to do all of this by hand, but luckily, I've created a calculator that does most of the calculations for you (it even calculates how your calories are in terms of protein, carbohydrates, and fat, depending on your goal). Check it out here.

The reason I said the calculator does most of the math for you is that once you know how many calories and grams of protein, carbohydrates, and fat you should be eating per day to meet your goals, Still need to convert those numbers into a meal. Plan on foods that you enjoy.

Read these articles to learn how:

The definitive guide to effective meal planning

How to Create Nutrition Plans That Are Suitable for Any Diet

Meal prep made easy: How to make the perfect meal prep

And if you need help with this process, check out Legion's custom meal planning serviceor our ready-made menu templates for Men and Women.

+ Scientific references

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