Calculating body mass index

Can anyone help me,Does anybody know how one calculates one's Body Mass Index. I believe it helps in calculating fitness levels but I would like to know about it. I have tried to access information from RW but with no luck.


  • weight in kg divided by height in metres squared.
    i.e I am 53kg and 1m 63 = 53/2.6569 = 19.95

    hope this helps,

    or look on
  • have a calculator where you can input height & weight in metric or imperial, and it calcualtes it for you.
  • There was a thread on the Stockholm marathon forum about this recently (didn't get too stuck into it - one forum habit is bad enough!) Anyway, there is an elite runner who has a regular presence there and who claims BMI is one of the key factors for elite long distance runners, who should aim, over a period of years, to reach 18-19. That would be lower than is healthy for most people.

    It's interesting that until you posted this Spiderman I don't recall there being much debate about optimum BMIs for runners.

    Any thoughts?

  • Thanks all for that. I have been very interested in 'doing things right' in terms of training lately. I have been an ardent dyed in the wool marathon man in the past and I'm afraid I let things slip a little until recently. I had multiple heart attacks in March this year, due to an inferior myocardial infarction (basically a blockage of an artery feeding blood to the heart muscle). Since having an angioplasty with 2 stents , which cleared the block I have been back to training with a vengence. I have a target of running the Dorset Three Peaks Challenge this October with a half-marathon scheduled for next year. But due to the recent health problems I have been interested in learning all about health issues and how to calculate my level of fitness and to monitor it. Any other ideas?
  • Surely BMI is slightly irrelevant for those doing regular sport as muscle weighs more than fat so they would have higher BMI's - isn't body fat perccentage a better gauge?
  • Gillian. How does one work out body fat percentage or does this require special scales or other equipment?
  • You can buy scales that do it for you - I got mine done at the gym by the instructor so I'm not sure of the calculations - he used calipers to 'pinch' various areas and then did his calculations.
    Sorry to be so vague ( I know Boots sell the scales although I think their ones only calculate your lower body fat percentage)
  • The stand-on scales aren't the best electronic tools, it's better to use the ones that measure through from foot to hand while you're lying down. Some gyms use these and so do BUPA. However, the fat calipers can be more accurate in the hands of an experienced person. There are other ways to measure fitness though eg. step test for heart rate recovery time, sit ups for core strength, grip strength measurement, sit & reach for flexibility, VO2max. A good gym should be able to offer a selection but decide which aspect of fitness you want measured.

    On the BMI front, if I were aiming for 18-19 I'd have no body fat because the weight would equal my current lean muscle mass! I had my fat content measured by calipers recently.
  • Karen I'm being a bit think (it is Friday after all) but I'm 1 metre 63, weigh 53kg - but my body fate percentage was measured as 15.5% using calipers - can that be correct as I calculate my BMI to be about 19/20?
  • sorry, fat not fate!! - see I said I was being a bit thick!!
  • BMI is only useful as a very rough guide. As Gillian says, if you excercise regularly you will have less fat and more muscle (muscle weighs around 7 times more than fat (I think, it's been a while since my lipid chemistry days). If you are tall and muscular you would probably have a BMI of 28 or more, which would indicate that you're overweight! The best way is to look in the mirror.
  • I read about Gillians method in association with the report last week about obesity in children.

    However I thought it should be different for men and women (ladies have extra fat layer).My wife has got soem of those hand held thingamijigs that does it all, and you input all pertinent data (sex,weight,height).This gives me a reading of just under 20% which is about right (I'm 6ft and 12st10).

    According to those height/weight charts I'm borderline obese.
  • BMI is purely a ration of height to weight. Insurance companies use it as a rough indicator of whether you are likely to croak. A BMI between 20-25 is considered desireable. Too low means you're Geri Halliwell, and we don't want to get on to her again (do we...??). Percentage body fat is a different thing and from previous threads, I think the consensus was that the scales are rubbish and an experienced person with calipers is your best bet. These things are always very general and take no account of body morphology etc. so best not to get too hung up on them.

  • BMI/calories burned/BMR :

  • Gillian, sorry for the delay in getting back to you. As others have said BMI is only a general indicator, it just relates height and weight to each and doesn't take into account whether your weight has more or less fat or muscle in it. Your BMI is borderline underweight and your fat content is below what is generally accepted as being healthy. You do need a certain amount of fat for a healthy life eg. some vitamins are fat-soluble and many female hormones are linked to fat in order to function.
  • Thanks Karen,

    I realise that my BMI is borderline and my doctor has told me not to lose any more weight ( I have regular chack ups as I have crohn's) I have a chack up next Tuesday and he wanted me to have gained wight by then as apparently I need some reserves in case I have another'attack' .
    It's difficult finding a balance between being healthy, being the way I'm happy with and also havig enough energy to do as much exercise as I'd like - but I think I'm getting there.
    thanks again
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