BMI Calculator

Enter your height and weight to instantly see your BMI (Body Mass Index) and the corresponding WHO health category. Supports both metric (kg/cm) and imperial (lb/ft+in) units.

Unit system

Height (cm)

Weight (kg)

Age (optional)

Sex (optional, for ideal weight)

Your BMI—

Category—

Healthy weight range—

Ideal weight (Devine)—

BMI scale (WHO)

15 18.5 25 30 35 40

Underweight < 18.5 · Normal 18.5–24.9 · Overweight 25–29.9 · Obese ≥ 30

Features

Metric (kg/cm) and imperial (lb/in)

WHO health category

Visual BMI scale

Healthy weight range for your height

Instant real-time calculation

How to Use

1. Choose your unit system: metric or imperial.

2. Enter your height and weight.

3. Your BMI, health category, and healthy weight range appear in real time.

4. Optionally enter age and sex to estimate ideal body weight using the Devine formula.

5. The colour bar below shows which health range you fall into.

About this tool

Body Mass Index is weight in kilograms divided by height in metres squared. It is a quick screening number used by the World Health Organization to group adults into underweight (below 18.5), normal (18.5–24.9), overweight (25–29.9) and three classes of obesity. This calculator works in metric or imperial units, places your result on the WHO scale, and shows the weight range that would put you between 18.5 and 24.9 for your height. If you add sex, it also estimates an "ideal" weight with the Devine formula that clinicians use for medication dosing. BMI does not measure body fat, muscle or where fat is stored, so treat it as a starting point for a conversation with a doctor, not a diagnosis.

Frequently Asked Questions

How is BMI calculated?

BMI = weight (kg) ÷ height (m)². For imperial units the tool converts pounds and feet/inches to kilograms and metres first, so 160 lb at 5 ft 9 in gives a BMI of about 23.6 in either unit system.

Is BMI accurate for athletes, older adults, or children?

Not very. Muscular people can score as overweight while being lean, and older adults can have a normal BMI with little muscle. Children and teenagers need age- and sex-specific percentile charts, which this adult calculator does not use.

What does the healthy weight range mean?

It is the range of weights that would give a BMI between 18.5 and 24.9 at your height. It is a population guideline; a doctor may recommend a different target based on your health, build and history.

What is the Devine ideal weight?

The Devine formula estimates ideal body weight as 50 kg (men) or 45.5 kg (women) plus 2.3 kg for every inch above 5 feet. It was designed for drug dosing, not as a personal goal, so it is shown only as extra context.

Are the cut-offs the same for everyone?

This tool uses the standard WHO adult categories. Some health authorities, particularly in Asia, use lower thresholds for overweight and obesity because health risks rise at lower BMI in those populations.