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A Simple and Accurate BMR Calculator (and How to Use It)

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A Simple and Accurate BMR Calculator (and How to Use It)

If you want to gain mastery over your weight and body composition, then you want to know how to calculate your BMR. This article breaks it all down.

 

“Calories don’t count.”

“A calorie isn’t a calorie.”

“Calorie counting doesn’t work.”

“What you eat is more important than how much.”

These are some of the most harmful diet lies told by trainers, fitness magazines, and self-styled “gurus.

Allow yourself to be duped by them and you’ll struggle with your weight and dieting for the rest of your life.

Learn the truth, however, and you’ll know how to lose weight with ease while also eating foods you actually enjoy.

A big promise, I know, but it’s not an exaggeration.

And it all starts with learning about and calculating your basal metabolic rate.

What is the Basal Metabolic Rate (BMR)?

basal metabolic rate

Your basal metabolic rate is the amount of energy your body burns at rest.

It’s the minimum amount of energy it costs to stay alive.

It’s called this because basal means “forming a base; fundamental” and metabolic means “related to the metabolism,” which is “the physical and chemical processes in an organism by which it produces, maintains, and destroys material substances, and by which it makes energy available.”

BMR is often expressed in calories, which is a measurement of energy. One calorie is the amount of energy it takes to heat one kilogram of water one degree Celsius (also called a kilocalorie).

For example, I’m 31 years old, 6’2 and 190 pounds and my BMR is about 2,200 calories.

I say “about” because BMR calculation formulas like what you’ll find in this article aren’t 100% accurate for everyone.

That said, they’re accurate enough to be practically useful for diet and meal planning.

Except in the cases of extremely high amounts of physical activity, your basal metabolic rate accounts for the majority of the energy your body burns every day.

That is, unless you’re very physically active, your basal metabolic rate burns more calories than your exercise and other activities.

This is why keeping your metabolism functioning optimally is a big part of successful long-term weight loss.

Use this workout and flexible dieting program to lose up to 10 pounds of fat and build muscle in just 30 days…without starving yourself or living in the gym.

Basal Metabolic Rate vs. Resting Metabolic Rate

rmr calculator

If you’ve heard of basal metabolic rate, you’ve probably heard of resting metabolic rate too.

What’s the difference?

Well, resting metabolic rate is the amount of energy your body burns in a relaxed, but not completely inactive state.

You see, basal metabolic rate is a reflection of how much energy your body would burn if you were to lay motionless for a day, without food.

Resting metabolic rate is a looser approximation of energy expenditure that accounts for eating and non-stressful movement.

Practically speaking, you can use either your basal or resting metabolic rate to help calculate how much food you should be eating.

How Does Basal Metabolic Rate Relate to Weight Loss?

bmr calculator to lose weight

The thing that most dictates whether you gain or lose weight is energy balance.

Energy balance is the relationship between the energy you feed your body and the energy it expends.

And as you now know, your basal metabolic rate accounts for a large portion of your daily energy expenditure.

Thus, your basal metabolic rate “drives” your weight loss efforts.

You see, the scientifically validated, “boring” reality is this:

  • Meaningful weight loss requires you to expend more energy than you consume.
  • And meaningful weight gain (both fat and muscle) requires the opposite: more consumption than expenditure.

If you’re shaking your head, thinking I’m drinking decades-old Kool-Aid, let me ask you a few questions.

Why has every single controlled weight loss study conducted in the last 100 years…including countless meta-analyses and systematic reviews…concluded that meaningful weight loss requires energy expenditure to exceed energy intake?

Why have bodybuilders dating back just as far…from Sandow to Reeves and all the way up the line…been using this knowledge to systematically and routinely reduce and increase body fat levels?

And why do new brands of “calorie denying” come and go every year, failing to gain acceptance in the weight loss literature?

The reality is a century of metabolic research has proven, beyond the shadow of a doubt, that energy balance, which operates according to the first law of thermodynamics, is the basic mechanism that regulates fat storage and reduction.

That doesn’t mean you have to count calories to lose weight…but it does mean you have to understand the relationship between calorie intake and expenditure and weight gain and loss.

How Do You Calculate Your BMR?

how to calculate BMR

The most accurate way to calculate your basal metabolic rate is to go to a lab and hook yourself up to a metabolic cart.

Fortunately, though, there are mathematical equations that can predict its results with a fair amount of accuracy.

The Harris-Benedict Equation

harris benedict bmr calculator

In the early part of the 20th century, Francis Benedict lead a number of studies on the human metabolism.

The result was the Harris-Benedict equation, which was published in 1919.

Here’s how it looked:

BMR calculation for men (metric) BMR = 66.5 + ( 13.75 x weight in kg ) + ( 5.003 x height in cm ) – ( 6.755 x age in years )
BMR calculation for men (imperial) BMR = 66 + ( 6.2 x weight in pounds ) + ( 12.7 x height in inches ) – ( 6.76 x age in years )
BMR calculation for women (metric) BMR = 655.1 + ( 9.563 x weight in kg ) + ( 1.850 x height in cm ) – ( 4.676 x age in years )
BMR calculation for women (imperial) BMR = 655.1 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) – ( 4.7 x age in years )

Subsequent decades of metabolic research conducted resulted in a revision to the formula in 1984, to this:

Men BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) – (5.677 x age in years)
Women BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) – (4.330 x age in years)

The Mifflin-St Jeor Equation

weight loss calculator

The Mifflin-St Jeor equation was introduced in 1990 by scientists from the University of Nevada to address some of the shortcomings of the Harris-Benedict equation.

Namely, its tendency to overestimate actual energy expenditure.

Here’s the equation:

Mifflin-St-Jeor bmr calculator(where s is +5 for males and −161 for females)

The Katch-McArdle Equation

ideal weight calculator

The Harris-Benedict and Mifflin-St Jeor equations are based on body weight, which means they don’t take into account differences in body composition.

This matters because muscle is metabolically active whereas body fat isn’t.

(Someone with a lot of muscle burns more energy at rest than someone with little muscle but a lot of fat.)

Thus, other formulas were created to fill this need.

The most popular one in fitness circles is the Katch-McArdle equation:

Katch-McArdle-bmr calculator(where LBM is the lean body mass in kg)

Which BMR Equation Is Best?

bmr calculator for men

The reality is each of these formulas have flaws and none are going to calculate your BMR with 100% accuracy.

The good news is that doesn’t matter. You don’t need to know it down to the calorie to achieve your goals.

You start with equations and, in time, learn your body’s actual calorie ranges for losing, maintaining, and gaining weight.

For example, some people find their metabolisms are quite a bit faster than equations predict and others quite a bit slower.

This is normal.

Now, some people recommend the Mifflin-St Jeor equation if you’re of average musculature and the Katch-McArdle if you’re more muscular than the average person.

There’s nothing wrong with this advice but I keep it simple and just advise using the Katch-McArdle.

It will give you a good starting point for caloric intake and that’s all you’re really looking for.

The BMR Calculator

bmr calculator activity level

Now that you understand what the BMR is and the equations used to predict it, let’s get to the actual calculator.

This uses the Katch-McArdle equation.

BMR

So…you now know your BMR.

What’s next? How do use this newfound knowledge to lose fat and build muscle?

Check out this article to find out.

The Bottom Line on BMR Calculators

best bmr calculator

When it comes to calculating your BMR, keep it simple and remember it probably isn’t 100% accurate.

You’re looking for a starting point for your meal planning, not a definitive judgment on your metabolic health

You’ll probably find through actual experience that your body burns a bit more or less energy than formulas predict, and this is especially true when you start factoring in calories burned through working out and moving in general.

So, use this BMR calculator to determine a caloric baseline, turn it into a well-designed meal plan, adjust as needed, and you’ll reach your goals.

What’s your take on BMR calculators? Have anything else to share? Let me know in the comments below!

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  • Thanks for stopping by and checking out my article! I hope you enjoyed it.

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  • wong jing wen

    Hey Mike, thanks for the great post.

    Just wanted to seek your advice. Base on the calculator above my BMR is around 1761 calories. I am weighing in at 77-78 currently and consuming around 2000 calories per day. I am working out 5 days split according to the BLS program and 2 days of cardio (basketball). With the amount of activity that i have should i reduce my calorie intake below the BMR. Or i should wait until my weight stop decreasing with current calorie consumption.

    • Welcome!

      I don’t recommend reducing cals unless you’re not getting results. As long as you’re losing 1-2 pounds a week, keep the cals the same.

      I also don’t recommend going below BMR. If you find yourself needing to eat at or below BMR to lost 1-2 pounds a week, you should reverse diet:

      http://www.muscleforlife.com/reverse-diet/

      LMK what you think.

  • Angelo

    Hello Mike,

    I have a question unrelated to the article but I don’ know where I can ask it . So I ask it here haha

    Have you ever thought to translating BLS ? I’m sure that many people will buy it here in Belgium and France if it was in French . ( I have BLS but I can’t give it to my friends because they don’t understand English haha)

    If you want , I can even translate it for you haha

    Keep going with these amazing articles and have good day.

    • Hey man!

      Yeah definitely I’m working on various foreign rights deals. Germany is already done working on France. 🙂

      Thanks brother.

  • dave

    Hey Mike,

    I think your calculator is quite accurate, its saying my BMR is about1800 and im on 2100 deficit at the moment and going strong. My query is about my father. Im trying to get him on BLS and sort his eating habits out especially since reading your article on visceral fat. I never understood how someone could not have that much fat anywhere else but the stomach and that article scared me a bit. He is 280 pounds and its all visceral fat because he is very strong and only carrying the beer belly weight basically. I know you said before about obese people, that changing there habits is the first real step for them. (he loves his beer and transfatty foods at the weekends.) I was wondering if he could follow the same meal plan i made myself as I find it very easy to follow and have no hunger energy issues etc. But would 2100 be too little calories for a guy his weight? Its strange how bad habits over years have literally left him like a child needing to be told to follow specific instructions on how to eat. BLOWS MY MIIIIND haha! – rambling aside, which calculator would be the best for him

  • Anthony

    Hey Mike great article if you really want to go to that ‘next step. This may sound a little silly to ask but what does the ‘P’ stand for in the P=370 and why does it equal 370? Also the 21.6 what does that stand for? Again apologies if i’ve missed the explanation but i feel if i know this i feel i could master the equation.
    Much appreciate your time on this dude have a good one.

    • Anthony

      Hey Mike sorry to be a pain but if you could get back to me on my silly query i’d be more than grateful. 🙂

      Chat soon bud

    • If you really want to dive deep into the science, this breaks it all down:

      http://www.amazon.com/Exercise-Physiology-Nutrition-Energy-Performance/dp/1451191553

      • Anthony

        Thanks Mike i’ll check it out. Btw just bought your ‘Muscle Myths’ book and i find myself nodding so far lol is there a preferable order which books to read first. Thanks again buddy

        • Thanks brother. Haha nodding as in bored or? I’m always open to feedback.

          I would say BLS is the best place to start.

  • Kay

    Hi Mike,

    I have a question for you regarding BMR and RMR. You base your caloric need calculations on an estimated BMR. I recently had my RMR (not BMR) measured, however, and I’d like to use that to base my caloric needs, both because I have the number and because my RMR is only about 100 calories higher than what the Harris-Benedict revised calculation predicts for my BMR, which suggests that my actual BMR would be somewhat lower than predicted.

    I haven’t yet calculated my BMR using the alternate formula because I don’t know my body fat percentage, though I would guess via BMI I’m probably in the low 20’s.

    Is there a rule of thumb, or a calculation I can use, to figure out how to more accurately determine my BMR from my RMR?
    I’m pretty fit (only about 5 lbs heavier than my ideal, healthy weight) and my goal is to slim down a bit (lose fat) while gaining a bit more muscle, so I’m trying to not pay too much attention to the scale, but I am trying to fine tune my diet to support fat loss/muscle maintenance or gain, both in caloric intake and protein optimization, so that I can be pretty sure that I’m making body re-composition progress and I’m not stuck in a plateau while I wait to see if my measurements change over a few week’s time.
    Thanks in advance for your guidance!

    • BMR and RMR are close enough that you can just work with your RMR (multiply it accordingly, adjust based on how your body responds, etc.).

  • Debra Blouin

    How do you explain weight gain which cannot be attributed to either an increase in calories or decrease in energy expenditure? Is there another condition which precipitates weight gain outside the energy balance hypothesis.

  • Charis

    my BMR Is appeerntly 1032 which seems extremely low

    • It’s possible! If you entered your weight and BF% correctly, that’s what it is.

  • Samuel Lewis

    Hello Mike. I am getting somewhat confused. I bought two books, BLS, and the Shredded Chef. My confusion is this: BLS says if youre over 30% bodyfat, to determine your TDEE, and that number is how you calculate your macros using 40% protein, 30% fat and 30% carbs. I never see in that section of the book where I should be making a 20% to 25% deficit, like I read on the other Legion site. So ultimately, if I am over 30% bodyfat, should I be cutting 20 to 25% of my calories from my TDEE?

    • Sorry about the confusion and thanks for picking up my books!

      Yep, whenever cutting, I recommend a 20-25% deficit. What changes is the macros if you’re above 25% BF (30% BF for women). I talk about this here:

      https://legionathletics.com/diet-meal-plans/

      Hope this helps! LMK what you think.

      • Samuel Lewis

        Ok that makes sense. Create the deficit using 40/30/30. My last issue on this journey is this; using the calculators has my bmr at 1805, tdee at 2166. 20% of that tdee puts me under my BMR, which I read as being bad. Since my bodyfat is so high, does that make it ok to be below BMR?

        • Hmm. That can happen if your activity level isn’t high enough. So, my first recommendation is to increase your activity level which will increase your TDEE hence increase your cutting cals.

          If that’s not possible, just eat at BMR.

  • Vincenzo

    Hey Mike, my BMR is about 1800 calories. I do heavy compound lifts 3 days per week and play soccer the 4th day. I eat 2000 calories a day but am still so hungry even with hitting my macros. Any suggestions?

  • sakib800

    Hey Mike is it inherently bad to eat below BMR? I cant seem to lose the fat fast enough, im somewhere around 13%-10% and I feel that I eat at my BMR or slightly below. So does this mean that Im actually not eating at my BMR becasue I hit the gym and cant seem to shed these last few pounds fast enough.
    THanks

    • Yeah… How’s your activity looking? Packing in the HIIT? Light cardio on top of that?

      • sakib800

        weights and maybe at least 10 minutes cardio everyday (heavy resistance on bike) or maybe I am not being patient? i wanna lose 2 pounds a week and i feel like i am losing little less than half of that and then on the weekends somehow gaining it all back.

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