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How To Calculate Your BMR

By | Last update: 23 July 2018

We've previously discussed how to calculate your BMI and WHR. Now, it's the turn of BMR (basal metabolism rate). In this article, Becky Kleanthous introduces the concept of BMR, shows you how to calculate your BMR and takes you through an example calculation using the measurements of King Henry VIII.

You've almost certainly heard of your BMI, the figure representing the relationship between your height and weight, but have you heard of your BMR? These three little letters could provide the information you need to kick-start a successful weight-loss regime (and sorry, but no: they do not stand for 'Biscuits Make you Ravishing', or 'Bring More Rum!')

Calculating calories with smartphone app

What's a BMR?

BMR is short-hand for 'basal metabolism rate', but it could just as easily mean 'Breathing, Making cells, Resting' because that's all it really refers to. Your body requires a certain amount of energy from calories in your food in order to do all the clever body stuff it does behind the scenes, without you even needing to think about it. Everyone is different, and all bodies need a slightly different amount of calories to get them through the day, even if they are simply lying in bed and watching box-sets back-to-back. Your heart still needs to pump; your lungs still inflate and deflate; your hair grows and your wounds heal. This all requires energy.

Just having the knowledge of your BMR could give you a deeper insight into tailoring your diet for your own body's needs. Somebody with a clean bill of health could consume 90% of their BMR and already be on their way to weight loss, even before adding in extra exercise. Of course, as with anything that involves tinkering with your temple - your body, that is - do seek medical guidance to ensure that the changes are safe and suitable for you.

Some BMR history...

In 1919, the Harris-Benedict formula was created to calculate BMR. It's since been superseded, so we will be working with the new and improved version, the Mifflin - St Jeor BMR formula, which was established in 1990.

And just before you start...

BMR is not infallible. It does take into account more factors than your BMI, but the equation doesn't know whether your mass comes from muscle or fat. Maintaining muscle burns more calories, so the BMR may emerge slightly lower than a beefy, brawny person's actual needs. Equally, someone with a super soft stomach will find their BMR is slightly higher than they really need.

The formula for BMR

The BMR formula:

The Mifflin - St Jeor BMR formula is as follows (separated for men and women and also metric and imperial):

MEN: BMR formula (metric)

BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5

MEN: BMR formula (imperial)

BMR = (4.536 × weight in pounds) + (15.88 × height in inches) - (5 × age) + 5

WOMEN: BMR formula (metric)

BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

WOMEN: BMR formula (imperial)

BMR = (4.536 × weight in pounds) + (15.88 × height in inches) - (5 × age) - 161

Give it a go and work out your BMR with the BMR calculator.

An Example:

King Henry VIII's armour reveals that he had a 52 inch waist at the time of his death, aged 55. Standing around 6 foot 1 inches tall, we can estimate his weight at around 300lbs.

Henry's BMR would use the following calculation:


BMR = (4.536 × weight in pounds) + (15.88 × height in inches) - (5 × age) + 5


(4.536 x 300) + (15.88 x 73) - (5 x 55) + 5


1360.8 + 1159.24 - 275 + 5

= 2250.04

So Henry's BMR would have been around 2250 at the time he died, which would have covered all his body's energy expending needs during a day of doing absolutely nothing whatsoever. Perhaps somebody could have mentioned this to the royal kitchen, who were providing at least 5000 calories a day for him to shovel down.

I hope you've enjoyed this article. If you would like some more information on the Harris-Benedict formula and and the Mifflin - St Jeor formula, take a look at our BMR formula article.

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