BMI Calculator
Works out your BMI and the weight range counted as healthy for your height.
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The formula
BMI = weight in kg ÷ (height in m)² BMI Prime = BMI ÷ 25
BMI Prime compares your BMI with 25, the top of the healthy range, so 1.00 sits exactly on that line.
What to watch out for
WHO adult categories: underweight below 18.5, healthy weight 18.5 to 24.9, overweight 25 to 29.9, obesity 30 or above. NICE uses lower cut-offs for people with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background: overweight from 23 and obesity from 27.5.
BMI does not measure fat. Muscular people can read high, and older adults who have lost muscle can read low. Children need age- and sex-specific growth charts instead.
Frequently Asked Questions
How do I work out BMI?
Divide your weight in kilograms by your height in metres, squared. At 70 kg and 1.75 m that is 22.9.
What weight is healthy for my height?
A BMI of 18.5 to 24.9. At 1.75 m that is 56.7 to 76.3 kg.
What is BMI Prime?
Your BMI divided by 25. A BMI of 22.9 gives a BMI Prime of 0.91, and anything above 1.00 is over the healthy range.
Is BMI accurate for everyone?
No. It is a screening figure for groups of adults and says nothing direct about body fat, muscle or health. Risk at the same BMI also differs by ethnicity and age.