BMI Calculator

How to use the bmi calculator

1. Choose metric or imperial units.
2. Enter your height and weight.
3. Read the BMI value and the category it falls in.

About this tool

Body mass index is weight in kilograms divided by height in metres squared. It was designed in the nineteenth century to describe populations, not individuals, and it remains useful for that: at scale it correlates well with body fat and with health outcomes.

For one person it is a crude screening number. It cannot distinguish muscle from fat, so athletes register as overweight; it ignores where fat is carried, though abdominal fat carries most of the metabolic risk; and the category boundaries were derived largely from European populations, with lower thresholds recommended for people of South Asian descent. Read the result as one input among several, not a diagnosis.

Common uses

• Getting a rough reference figure before a check-up.
• Seeing the healthy weight range for a given height.
• Converting between the units a form asks for.

Frequently asked questions

What are the standard BMI categories?

Below 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30 and above obese. Some guidelines use lower thresholds for South Asian populations.

Is BMI accurate for athletes?

No. Muscle is denser than fat, so a muscular person can have a high BMI and low body fat. BMI does not measure composition.

Is this medical advice?

No. It is a calculator. Discuss any concern about your weight or health with a qualified clinician.