BMI Calculator

What Is a BMI Calculator?

A BMI calculator is a tool that uses a person's height and weight to calculate their Body Mass Index (BMI). BMI is a commonly used screening measure for adults and can provide a general indication of whether a person's weight falls within a particular BMI category.

The YesTools BMI Calculator supports both metric and imperial measurements. You can enter your height and weight in centimetres and kilograms, or in feet, inches, stones and pounds. The calculator converts the measurements where necessary and provides the resulting BMI to one decimal place.

Why Use the BMI Calculator?

The BMI Calculator provides a quick way to calculate BMI without requiring manual calculations. It is designed to be simple to use on desktop and mobile devices.

How to Use the BMI Calculator

Calculating your BMI takes only a few seconds. Choose a measurement system and enter your height and weight.

1. Choose your units — Select Metric for centimetres and kilograms, or Imperial for feet, inches, stones and pounds.
2. Enter your height — Provide your height using the appropriate fields for the selected measurement system.
3. Enter your weight — Enter your current weight using kilograms for Metric or stones and pounds for Imperial.
4. Calculate your BMI — Select Calculate BMI to display your BMI value and the corresponding adult BMI category.

How Is BMI Calculated?

Body Mass Index is calculated by dividing weight in kilograms by height in metres squared. The standard formula is BMI = weight (kg) ÷ height (m)². The result is a numerical value that can then be compared with commonly used adult BMI categories.

For example, an adult weighing 70 kilograms with a height of 1.75 metres has a BMI of approximately 22.9. This falls within the commonly used healthy-weight BMI range for adults.

Adult BMI Categories

For adults, a BMI below 18.5 is commonly classified as underweight, 18.5 to 24.9 as healthy weight, 25.0 to 29.9 as overweight, and 30.0 or above as obesity. These categories are general screening classifications rather than individual medical diagnoses.

Metric and Imperial BMI Calculations

The BMI formula uses kilograms and metres regardless of the measurement system entered. When imperial measurements are selected, the calculator converts the entered height and weight into the appropriate metric values before calculating BMI. This means the same BMI result is produced whether equivalent metric or imperial measurements are entered.

Understanding Your BMI Result

BMI is useful as a population-level and individual screening measure, but it has important limitations. It does not directly measure body fat and does not distinguish between muscle, bone, fat and other body tissues. As a result, BMI should not be considered a complete assessment of an individual's health.

BMI categories can also be less appropriate for certain groups. Children and teenagers require age- and sex-specific assessment, while pregnancy requires different considerations. People with high levels of muscle mass may also have a higher BMI without having excessive body fat. For personalised interpretation of BMI or concerns about weight and health, consult a qualified healthcare professional.

Frequently Asked Questions