BMI Calculator

BMI is your weight in kilograms divided by the square of your height in metres. At 170 cm and 65 kg that is 65 ÷ 1.7², or 22.5. The arithmetic is trivial; what actually matters is which threshold table you read it against, because the cut-offs used in Europe and North America differ from those used across much of Asia.

How to use

1. Enter your height in centimetres — decimals such as 170.5 are fine.
2. Enter your weight in kilograms. Body weight swings by a kilo or two through the day, so a morning reading before eating is the most comparable.
3. Read the resulting index and the band it falls into.
4. If you are tracking change over time, only compare readings taken at the same hour on the same scale.

When you actually need this

• Checking which band the BMI printed on a medical report belongs to.
• Working backwards from a target band to see how many kilos separate you from it.
• Filling in an insurance application or a clinic intake form that asks for BMI.
• Comparing a figure quoted in pounds and feet against the metric bands everyone else uses.

Thresholds and their limits

The WHO bands are: under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, and 30 or above obese. Asia-Pacific guidance, including the Korean Society for the Study of Obesity, lowers those to 23 for overweight and 25 for obese, because metabolic risk rises at a lower index in those populations. BMI cannot tell muscle from fat, so a trained lifter often lands in the overweight band while an older person with little muscle can sit in the normal band with a high body fat percentage. For children and teenagers the raw number is not used at all — age-and-sex percentile charts are — and during pregnancy the pre-pregnancy weight is the reference.

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FAQ

What formula does BMI Calculator use?

It uses the standard published formula for this calculation, applied exactly as written with no rounding until the final result. The inputs you provide are the only variables — there are no hidden assumptions or regional adjustments.

How accurate is the result from BMI Calculator?

The arithmetic is exact to the precision your browser supports. Accuracy in practice depends on your inputs: an estimate built on rounded figures will itself be an estimate, so enter the most precise values you have.

Can I use this for official or financial decisions?

Treat the output as a well-calculated estimate rather than professional advice. For medical, tax, legal or lending decisions, confirm the figure with a qualified professional or the institution involved before acting on it.

Read the full guide: how to use BMI Calculator step by step →