BMI Calculator

Body mass index in metric or imperial, with the healthy range.

BMI Calculator

Fast online calculation engine

Height (cm)

Weight (kg)

BMI Score0.0Underweight

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What does BMI Calculator do?

Calculate body mass index from height and weight in either metric or imperial units. It shows your BMI, the WHO category it falls in, and the weight range that would place you in the healthy band for your height.

How to Use BMI Calculator

1
Choose your unitsSwitch between metric and imperial at the top.
2
Enter height and weightFeet and inches, or centimetres — whichever you know.
3
Read your BMIThe number, its category, and your healthy weight range.

Key Features

Metric (kg, cm) and imperial (stone/pounds, feet/inches) input
WHO category with a visual scale showing where you sit
The exact weight range that would be classed as healthy for your height
Devine ideal body weight shown as a second reference point
Honest explanation of where BMI is and is not a useful measure

Frequently Asked Questions

How is BMI calculated?

BMI = weight in kilograms ÷ (height in metres)². For imperial: (weight in pounds ÷ (height in inches)²) × 703. Both give the same number.

What are the BMI categories?

Below 18.5 is underweight, 18.5–24.9 is the healthy range, 25–29.9 is overweight, and 30 or above is obese, split into classes I, II and III at 35 and 40.

Is BMI accurate for everyone?

No. It measures weight for height, not body composition, so it overestimates risk for muscular people and underestimates it for those with low muscle mass. It is also less reliable for children, pregnant women, the elderly and some ethnic groups, where different thresholds apply.

Is this medical advice?

No. BMI is a screening indicator, not a diagnosis. Waist circumference, body fat percentage, blood pressure and blood markers all tell you more. Talk to a doctor before acting on any number here.

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