BMI Calculator

Body Mass Index is weight divided by the square of height — kilograms per metre squared — and the World Health Organization adult classification sorts the result into underweight, healthy, overweight and obese bands. Enter your height and weight in metric or imperial units to see your BMI, its category, and the healthy weight range for your height.

cm
kg
Your BMI —
Category —
Healthy weight for your height —
1518.525303540

BMI is a general screening tool, not a diagnosis. It does not account for muscle mass or body composition and is not intended for children, pregnancy, or athletes. For personal advice, speak to a healthcare professional.

How to Calculate BMI

Two numbers — height and weight — give your Body Mass Index.

1

Pick your units

Switch between Metric (centimetres and kilograms) and Imperial (feet, inches and pounds). Your entries convert automatically when you change units.

2

Enter height and weight

Type your height and weight. BMI is weight divided by height squared — kg/m² in metric, or 703 × lb/in² in imperial — and it updates instantly as you type.

3

Read your category and range

See your BMI, its WHO category on the colour scale, and the healthy weight range for your height so you know where you stand at a glance.

BMI doesn't distinguish muscle from fat — for a composition estimate, try the Body Fat Calculator.

BMI Categories for Adults

The cut-offs this calculator uses are the World Health Organization’s adult BMI classification.

CategoryBMI (kg/m²)
UnderweightBelow 18.5
Normal weight (healthy range)18.5 – 24.9
Overweight25.0 – 29.9
Obese (class I)30.0 – 34.9
Obese (class II)35.0 – 39.9
Obese (class III)40.0 and above

These bands come from the World Health Organization and apply to adults of both sexes; the calculator switches category at exactly 18.5, 25, 30, 35 and 40. Children and teenagers aged 2 to 19 are assessed on age- and sex-specific percentiles instead, so these fixed categories don’t apply to them. BMI is a screening estimate, not a diagnosis — see the note above the scale.

Frequently Asked Questions

How is BMI calculated?
BMI is your weight divided by the square of your height. In metric it is kilograms divided by metres squared (kg/m²). In imperial it is 703 times pounds divided by inches squared. This calculator does the maths for you in either unit.
What is a healthy BMI?
For adults the World Health Organization considers a BMI of 18.5 to 24.9 a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is in the obese range. Those cut-offs are the same for men and women, and the calculator labels your result against them as you type. They are population thresholds rather than a diagnosis: BMI cannot separate muscle from fat, so a very muscular build can land in the overweight band with no excess body fat at all.
Is BMI accurate?
BMI is a quick screening tool, not a diagnosis. It does not distinguish muscle from fat, so very muscular people can read as overweight, and it is not designed for children, pregnancy, or the elderly. Treat it as a starting point and talk to a clinician for a full picture.
What is a healthy weight for my height?
A healthy weight is any weight that puts your BMI between 18.5 and 24.9 for your height. Enter your height and this calculator shows that healthy weight range in kilograms or pounds. The range is worked out as 18.5 × height² and 24.9 × height² with height in metres, so at 1.75 m it runs from about 57 kg to 76 kg — roughly 125 lb to 168 lb. Because it scales with the square of your height, every extra 5 cm of height moves both ends of the range up by several kilograms.
Is BMI different for men and women?
No — BMI is not calculated differently for men and women. The BMI formula and the WHO weight categories are the same for both sexes, so a man and a woman of the same height and weight get the same BMI. At that same BMI, however, women typically carry a higher body-fat percentage than men. BMI is a general screening tool, not a body-composition measurement. The one exception is children and teens aged 2 to 19, where BMI is read as sex- and age-specific percentiles rather than fixed categories.

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