BMI Calculator

Calculate your Body Mass Index in metric or imperial units and see which WHO weight category it falls in. Private, free, and no signup required.

Height

Weight

About BMI Calculator

Body Mass Index (BMI) compares your weight with your height and places the result in a standard category. This calculator accepts metric (centimetres and kilograms) or imperial (feet, inches and pounds) measurements and shows your BMI value, the category it falls in, and where you sit on the BMI range.

BMI is a quick screening number, not a diagnosis. It cannot tell muscle from fat, and it does not consider age, sex or body composition. Use it as a conversation starter with a healthcare professional rather than as a verdict on your health.

How to use the BMI Calculator

Choose Metric (cm/kg) or Imperial (ft/lbs).
Enter your height. In imperial mode enter feet and inches.
Enter your weight.
Click Calculate BMI to see your value, category and position on the BMI range.

What it can do

Metric and imperial

Switch units without converting anything yourself.

Category result

Shows whether the value falls in underweight, normal weight, overweight or obesity ranges.

Visual range

A BMI range bar shows where your number sits between categories.

Private

Calculated in your browser; your measurements are not stored or sent.

When it is useful

Getting a quick baseline before setting a fitness or nutrition goal.
Tracking change over time as you adjust diet or exercise.
Preparing numbers to discuss with a doctor or dietitian.

Good to know

BMI = weight in kilograms divided by height in metres squared. The WHO adult categories are: under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, 30 and above obese.
Athletes and people with high muscle mass can have a high BMI without excess body fat.
BMI categories are different for children and teenagers, who are assessed against age and sex growth charts. This tool is for adults.
This tool does not give medical advice.

Read the guide: BMI Calculator Guide

Frequently Asked Questions

Q.How is BMI calculated?

Divide your weight in kilograms by the square of your height in metres. For example, 70 kg at 1.75 m gives 70 / 3.0625 = 22.9.

Q.What is a healthy BMI range?

For most adults, a BMI between 18.5 and 24.9 is classed as normal weight by the World Health Organization.

Q.Can I use this BMI calculator for children?

No. Children and teens are assessed using percentile charts for their age and sex. Ask a paediatrician or use a tool designed for children.

Q.Why is my BMI high even though I am muscular?

BMI uses only weight and height, so it cannot distinguish muscle from fat. Body fat percentage or waist measurement give a fuller picture.

Q.Does BMI work the same for all ethnic groups?

Not exactly. Some health bodies use lower thresholds for people of South Asian and some other backgrounds. Discuss the right targets with a healthcare professional.

Q.Is my data saved?

No. The calculation happens in your browser and your height and weight are not stored.

Q.How often should I check my BMI?

Weight naturally fluctuates, so checking every few weeks or months is enough to see a trend.