What is BMI Calculator?

The BMI Calculator computes your Body Mass Index from height and weight to help assess if you are in a healthy weight range. This free tool supports both metric and imperial units — all calculations happen privately on your device.

Toggle between metric (kg, cm) and imperial (lbs or stones, ft+in) inputs, and the calculator returns the BMI value plus the WHO category — Underweight, Normal, Overweight, or one of three Obesity classes. You also get BMI Prime, an optional waist-circumference risk readout, a coloured scale showing where you sit relative to each band, and a result you can copy straight into a fitness log or chat message.

How to use

1. Enter your weight in kilograms, pounds, or stones
2. Enter your height in centimeters or feet and inches
3. Click Calculate to see your BMI score and weight category

When to use

• Checking whether your current weight falls in the standard healthy range for your height.
• Logging a baseline before a diet or training programme so progress is easy to compare.
• Filling out a clinic intake form that asks for BMI rather than raw height and weight.

Result

At 70 kg and 175 cm tall, your BMI is 22.9, which falls in the Normal weight category.

FAQ

Is BMI accurate for athletes or very muscular people?

Not always. BMI does not separate muscle from fat, so a heavily trained athlete can land in the Overweight band while having low body fat. For body composition, pair BMI with a waist measurement or a body fat estimate.

Which formula does the calculator use?

The standard WHO formula: weight in kilograms divided by height in metres squared. Imperial inputs are converted internally to kilograms and metres first, so the result is identical regardless of which unit you choose.

What BMI counts as healthy?

WHO considers 18.5 to 24.9 the Normal range for adults. 25 to 29.9 is Overweight; 30 and above is Obese, split into Class I, II, and III. Categories shift for children, older adults, and some ethnic groups.

Does this calculator work for children and teens?

Yes. Enter an age from 2 to 19 along with the child's sex and the tool switches to a CDC BMI-for-age percentile instead of the adult cutoffs, since healthy ranges differ at every age. Still confirm any reading with a paediatrician — a single number never replaces a growth-chart check.

Does the page send my height and weight anywhere?

No. The maths runs entirely on your device and nothing is transmitted. Numbers vanish when you close or refresh the page, so the calculator stays private even on a shared computer.

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