How to calculate your body mass index: weight (kg)/height (m) squared eg. 70kg/1.7m2 = 24.2 The World Health Organisation rates the normal BMI of an Asian should be between 18.5 and 23, and the proportion of Asians with a high risk of non-insulin-dependant (type two or adult-onset) diabetes and cardiovascular disease were those with a BMI higher than 23. BMI is only applicable to adults from 20 to 65 years of age, while children's health should be gauged on growth charts instead. Registered dietician Kitty Wong Kit-yee says BMI should be used as a health indicator rather than a means of justifying body sizes. People with a BMI of 23 (their weight in kilograms divided by their height in metres squared) or above are not necessarily 'fat'. If their muscle mass is heavy, they can still be considered healthy.