BMI calculator

Get your body mass index and category from height and weight.

Height (cm) Weight (kg)

Enter your height and weight.

BMI is a rough indicator and does not account for muscle mass or body type. Consult a professional for health decisions.

BMI is the number a health check-up prints next to your weight, and it is easy to see the figure without knowing what produced it or where the boundaries sit.

This calculator takes height and weight and returns a body mass index to one decimal place, along with the category it falls into. The category uses Asia-Pacific cut-offs, which are stricter than the international WHO ranges.

How it works

What you enter

Two fields: height in centimetres and weight in kilograms. Press Calculate, or just hit Enter in either field.

The formula

BMI = weight (kg) ÷ height (m)²

Height is entered in centimetres and converted to metres internally, so 172 cm becomes 1.72. Someone 172 cm and 68 kg gets 68 ÷ (1.72 × 1.72) = 23.0. The result is rounded to one decimal place.

The categories used here

BMI	Category
Under 18.5	Underweight
18.5 – 22.9	Normal
23.0 – 24.9	Overweight
25.0 – 29.9	Obese (class I)
30.0 and above	Obese (class II+)

These are the Asia-Pacific cut-offs, adopted because metabolic risk tends to appear at a lower BMI in Asian populations. The WHO international ranges place overweight at 25 and obesity at 30, so the same BMI of 24 reads as overweight here but normal on a chart using WHO values. Neither table is wrong — they are calibrated to different reference populations.

What BMI does not capture

BMI uses only height and weight, so it cannot tell muscle from fat. A trained athlete often lands in an "overweight" band while carrying little body fat, and someone with low muscle mass can sit in the normal band with high body fat. It is also not designed for children, pregnant women, or older adults, whose body composition follows different patterns. Treat it as a rough screening figure. For anything affecting a health decision, check with a doctor or another qualified professional.

Terms explained

BMI: Body mass index — weight in kilograms divided by height in metres squared.
Asia-Pacific criteria: A cut-off table that sets overweight at 23 and obesity at 25, lower than the WHO thresholds.
WHO criteria: The international table, with overweight at 25 and obesity at 30.
Body fat percentage: The share of body mass that is fat. BMI does not measure it and cannot distinguish it from muscle.
Waist circumference: A separate measure of abdominal fat, often used alongside BMI because BMI ignores where weight sits.

Frequently asked questions

How is BMI calculated?

Divide your weight in kilograms by your height in metres squared. This tool takes height in centimetres and converts it for you, so 172 cm and 68 kg gives a BMI of 23.0.

Why does this calculator say overweight at 23 instead of 25?

It uses the Asia-Pacific cut-offs, which set overweight at 23 and obesity at 25. They are lower than the WHO international ranges because metabolic risk tends to appear at a lower BMI in Asian populations, and both tables are in legitimate use.

Is BMI accurate for muscular people?

Not particularly. BMI works from height and weight alone and cannot separate muscle from fat, so people with a lot of muscle often land in an overweight band despite low body fat. Body fat percentage or waist circumference gives a fuller picture.

Does BMI apply to children or during pregnancy?

No. Children are assessed against age and sex growth percentiles rather than adult cut-offs, and BMI is not a meaningful measure during pregnancy. Ask a healthcare provider for the right measure in those cases.

What should I do if my BMI is outside the normal range?

Treat it as one screening number, not a diagnosis. Blood pressure, blood sugar, lipids, and waist circumference matter alongside it, so speak with a doctor for an assessment based on your full picture rather than acting on BMI alone.