July 14, 2026 Body Mass Index (BMI) Calculator

You may have heard of body mass index (BMI), but what exactly is it? And what does it have to do with diabetes?

The Basics of BMI

Every body has its own unique size and shape. BMI is a simple calculation that uses a person’s height and weight to designate a classification. The formula is BMI = kg/m²; kg is a person’s weight in kilograms and m² is height in metres squared.

BMI does not determine body fatness or general health. Body composition and distribution of body fat in people with similar BMIs can vary widely. It’s important to know that the BMI calculation is one of many used mostly by healthcare professionals to determine a person’s risk of developing health problems. Research suggests that a BMI above or below the normal weight range is associated with an increased risk of developing different chronic conditions.

A person’s level of risk, together with other assessment measures, will help guide recommendations for managing health. Measuring waist size (also known as waist circumference) is useful, since having a lot of fat around the waist is linked to greater health risks. Bottom line: BMI alone is not the measure of how healthy you are.

Calculate your Body Mass Index

Who is BMI for?

The BMI calculator applies to most adults 18-65 years old. It is less accurate for:

• Muscle builders
• Long-distance athletes
• Pregnant individuals
• Elderly populations
• Young children
• People with a physical disability
• People of certain ethnicities

Why?

BMI does not take into account whether your weight is muscle or fat. People with a higher muscle mass, such as athletes, may have a high BMI but do not have a greater health risk. Those with a lower muscle mass, such as children who have not completed their growth, or older people, who might be losing some muscle mass, may have a lower BMI. During pregnancy and lactation, body composition changes, so using BMI is not appropriate.

Diabetes and BMI

A BMI that falls within a category above “normal” is linked to an increased risk of developing type 2 diabetes, along with other chronic conditions like heart disease, hypertension and some forms of cancer. For people living with diabetes, certain medications, including insulin, can make managing their weight more challenging and can contribute to a higher BMI.

When used together with other indicators, BMI can help identify those who may benefit from obesity management. Talk to your healthcare provider about what is right for you.

Health risk classification according to body mass index

Classification	BMI category (kg/m2)	Risk of developing health problems
Underweight	< 18.5	Increased
Normal Weight	18.5 - 24.9	Least
Overweight	25.0 - 29.9	Increased
Obese class I	30.0 - 34.9	High
Obese class II	35.0 - 39.9	Very high
Obese class III	>= 40.0	Extremely high