BMI Calculator

BMI Calculator

Your Body Mass Index and weight category — instantly.

100% private Instant results No sign-up Updated Jul 28, 2026

About this tool

Calculate your Body Mass Index from your height and weight, see which category it falls into, and understand what the number does and does not tell you. Metric and imperial units supported.

How it works

BMI is a simple height-to-weight ratio designed for population screening. The tool rounds to one decimal place and maps the value to the standard WHO adult categories, while making clear that individual body composition can make BMI misleading for athletes, older adults and some ethnic groups.

How to use BMI Calculator

1Choose metric (cm and kg) or imperial (ft/in and lb) units.
2Enter your height and weight.
3View your BMI and the category it falls into.
4Read the honest guidance about what BMI can and cannot tell you.

Examples

A height of 175 cm and weight of 70 kg gives a BMI of 22.9 — in the healthy range.

A height of 5 ft 9 in and weight of 200 lb gives a BMI of 29.5 — overweight.

A BMI of 25 is exactly the boundary between healthy and overweight.

Pro tips

Measure your height and weight in the morning, before meals, for the most consistent reading.
BMI is a screening tool, not a diagnosis — athletes with high muscle mass can show a high BMI while being very lean.
For personalised guidance, discuss results with a healthcare professional.

Frequently asked questions

How is BMI calculated?

Metric: weight (kg) ÷ height (m)². Imperial: 703 × weight (lb) ÷ height (in)². The calculator handles both automatically.

What are the BMI categories?

Below 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30 and above obesity. These cut-offs are based on WHO guidelines for adults.

Is BMI accurate for everyone?

No. It does not distinguish muscle from fat and is not adjusted for age, sex or ethnicity. Treat it as one data point, not a health verdict.

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