How this calculator works
Weight is converted to kilograms and height to metres, then BMI = weight divided by height squared. The equation and the WHO cutoffs are the same for women and men; no separate female chart exists. BMI screening does not apply during pregnancy or lactation, when weight gain follows its own guidance, and the measure reflects neither body composition nor fat distribution. It is a screening tool for adults aged 20 and over. The result is an estimate for information only and is not medical advice.
Formula
BMI = weight in kilograms / (height in metres)², with WHO adult categories: below 18.5 underweight; 18.5 to 24.9 normal; 25.0 to 29.9 overweight; 30.0 and above obesity classes I to III.
Worked example
A woman weighing 66 kg at 1.64 m has BMI = 66 / 1.64² = 24.5, in the normal category. At 145 lb and 5 ft 4 in the result is about 24.9.
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Frequently asked questions
Is BMI interpreted differently for women?
The cutoffs are identical for both sexes. On average women carry more fat than men at the same BMI, but the screening categories stay the same.
Can I use this during pregnancy?
No. Weight gain in pregnancy is guided by pre-pregnancy BMI and stage of pregnancy, not by adult BMI categories. Use the pregnancy weight gain calculator instead.
What about Asian population cutoffs?
Some Asian populations use lower action points, near 23 for overweight and 27.5 for obesity. This page shows the standard WHO cutoffs; a clinician can advise on which apply to you.