What is a healthy BMI for my height?

Between 18.5 and 24.9 for adults, whatever your height — the bands are not height-adjusted. The calculator converts that back into a weight range in your own units so you can see what it means in practice.

Why is my BMI high when I am fit?

Because BMI only sees mass. A bodybuilder and a sedentary person of the same height and weight get an identical BMI and the same 'overweight' label. Use waist-to-height ratio or a body-fat measurement alongside it.

Does BMI work for children?

Not with these adult cut-offs. Children and teenagers are assessed against age-and-sex percentile charts, so a pediatric BMI-for-age chart is the right tool there.

Is this medical advice?

No. It is arithmetic on the numbers you enter. Any decision about weight, medication or a health condition needs a clinician who can see the things a BMI cannot measure.

Calculators & Converters Ready to use

BMI Calculator

Work out body mass index from height and weight in metric or imperial, with the WHO category, your healthy weight range, and body-fat and ideal-weight modes.

Weight

kg (metric) or lb (imperial)

Height

cm (metric) or inches (imperial)

Units

Mode

Age (body-fat mode)

Sex

This tool runs entirely in your browser. Your input never leaves your device.

About BMI Calculator

Body mass index is weight divided by height squared — 70 kg at 1.75 m is 22.9. It is not a measurement of body fat; it is a cheap population-level screen that correlates with it, computed from the two numbers everybody already knows. This calculator takes kilograms and centimetres or pounds and inches, and reports the result against the WHO bands: under 18.5 underweight, 18.5 to 24.9 normal range, 25 to 29.9 overweight, 30 and above obese.

Alongside the category it shows the weight range that would put your height inside the normal band, which is usually the more actionable number. Two further modes are on the same page: body fat percentage from the Deurenberg equation (BMI, age and sex), and ideal body weight from the Devine formula, the 50 kg plus 2.3 kg per inch over five feet rule that anaesthetists still dose with.

Both extras are approximations with known failure modes, stated rather than buried. BMI cannot tell muscle from fat, so it over-classifies trained athletes and under-classifies older adults carrying fat centrally; Deurenberg inherits that error and adds a sex term; Devine was derived for drug dosing in 1974 and ignores frame size entirely. Treat the numbers as a prompt for a conversation, not a diagnosis.