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BMI Calculator 100% Free

Calculate your BMI in seconds

Enter your height and weight to see your Body Mass Index, your WHO category, and the healthy weight range for your height.

Free No sign-up Private — runs in your browser
cm
100 cm250 cm
kg
25 kg300 kg

Age and sex never change your BMI number — they only add a short context note below.

Your Body Mass Index
24.2
Healthy
1418.5253040
Underweight < 18.5 Healthy 18.5–24.9 Overweight 25–29.9 Obese ≥ 30

How it works

BMI is a quick screening number based only on height and weight. Here is all this calculator does:

1

Enter your measurements

Type or slide to your height and weight — metric (kg, cm) or imperial (lb, ft/in). The result updates as you type.

2

We apply the BMI formula

BMI = weight in kilograms ÷ height in metres squared. Imperial values are converted to metric first, so the result is identical either way.

3

See your category and range

Your BMI is placed on the WHO scale, and we work out the healthy weight range for your exact height — plus how far you are from it.

Frequently asked questions

Quick answers about BMI and how to read your result.

What is BMI and how is it calculated?

Body Mass Index (BMI) is your weight in kilograms divided by the square of your height in metres: BMI = kg ÷ m². It is a simple screening measure used worldwide to classify adults as underweight, healthy weight, overweight, or obese.

What is a healthy BMI?

For adults, the World Health Organization (WHO) classifies a BMI of 18.5 to 24.9 as healthy. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese.

Is BMI accurate for athletes and muscular people?

Not always. BMI cannot tell muscle from fat, so very muscular people can score in the overweight range while being lean, and older adults can score "healthy" while carrying little muscle. Treat it as a rough guide, not a complete picture of health.

Does BMI work the same for children and teenagers?

No. For under-18s, BMI is compared against growth charts for their exact age and sex (called BMI percentiles), because children are still growing. The adult categories on this page apply to adults aged 18 and over.

Is this medical advice?

No. BMI is a general guide and a screening tool only — it does not diagnose any condition and does not account for body composition, pregnancy, or medical history. If you are concerned about your weight or health, please speak to a doctor or other qualified health professional.

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