Free

Free BMI Calculator

Enter height and weight for your Body Mass Index instantly — with a color-coded category and visual scale.

Free tool · No sign-up · Private

Height (cm)

Weight (kg)

Enter your height and weight above — your BMI and category appear instantly.

BMI is a screening measure, not a diagnosis — it doesn't account for muscle mass, bone density, or body composition. Talk to a health professional for personal advice.

Private by design. Everything runs 100% in your browser — your measurements are never uploaded, stored, or sent anywhere.

About this tool

About the BMI calculator

Body Mass Index (BMI) is the standard quick check relating weight to height: weight in kilograms divided by height in meters squared. It sorts adults into four WHO categories — underweight, normal, overweight, obese — used worldwide by doctors, insurers, and fitness programs as a first screening step.

This free calculator works in metric (cm/kg) or imperial (ft/in/lbs), shows your number instantly with a color-coded category, and plots it on a visual scale so you can see exactly where you land. Remember it's a screening measure: muscle mass, bone density, and body composition aren't captured, so treat it as a starting point, not a verdict.

How it works

Three steps to your BMI

Pick your units

Metric (cm/kg) or imperial (ft/in/lbs) — switch anytime, the result converts instantly.

Enter height & weight

Type your numbers. The BMI, category, and scale position update live as you type.

Read your result

See your number color-coded by WHO category, plotted on the 15–40 scale bar.

FAQ

BMI questions

How is BMI calculated?

BMI = weight (kg) ÷ height (m)². In imperial units it's 703 × weight (lbs) ÷ height (in)². Enter your numbers and the result appears instantly — no math needed.

What is a healthy BMI?

The World Health Organization defines 18.5–24.9 as the healthy range for adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese. These cutoffs apply to most adults regardless of age.

Is BMI accurate for athletes or muscular people?

Not always — BMI can't tell muscle from fat, so very muscular people can score as 'overweight' while being perfectly healthy. It's a screening tool, not a diagnosis. Body-fat percentage or waist measurements give a fuller picture.

Does BMI work for children?

Children's BMI is interpreted differently — against age- and sex-specific growth charts, not the adult cutoffs. This calculator uses adult categories; for kids, check with a pediatrician.

Is my data private?

Yes. The calculation runs entirely in your browser — your height and weight are never uploaded, stored, or sent anywhere.

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