|weight in kilograms|
|Body Mass Index (BMI) =||-----------------------------------------------|
|(height in metres) x (height in metres)|
e.g. today I'm 11st4lb = 158lb = 71.7kg (divide pounds by 2.2 to get kilograms)
and I'm 5ft10in = 70in = 1.78m (multiply inches by 0.0254 to get metres)
So my BMI = 71.7 / (1.78 x 1.78) = 22.6
In the UK the BMI is then graded as follows:
BMI over 30, you're obese. This is seriously unhealthy, do something about it now.
BMI between 25 and 30, you're overweight, you'd be well advised to do something about reducing it a little.
BMI between 20 and 25, you're normal, no need to worry.
BMI between 15 and 20, you're underweight. you'd be well advised to do something about increasing it a little.
BMI under 15, you're malnourished. This is seriously unhealthy, do something about it now.
I'm 22.6, that puts me right in the middle of the "normal" 20-25 range. HA! and you all thought I wasn't normal, didn't you!
If you think it's difficult to stay in such a narrow range, think again. At 5ft10in I'd be "normal" at any weight from 9st13lb (when my BMI would be 20) up to 12st6lb (when my BMI would be 25). That's a range of 2st7lb to remain at a healthy weight.
The above is the broad, easy formula that applies quite well to almost every otherwise healthy person EXCEPT CHILDREN so don't use this formula until you've stopped growing. There are also slight tweaks to the formula between men and women and with age, but for you lot the tweaks make little difference.