Accurate BMI Calculator

Accurate BMI Calculator

Body Mass Index

This may be the most accurate BMI Calculator online. It's designed to work out what your Body Mass Index is. Body Mass Index is a rule of thumb calculation that helps medical professionals in quickly working out if someone is classed as underweight, normal weight, overweight, or obese.

Try our Accurate TDEE Calculator to get your Total Daily Energy Expenditure.

The BMI calculation is applicable more to medical and public health professionals seeing trends in large populations, rather than a tool for individuals to work out if they are classed as a healthy body shape.

How do you calculate BMI?

The BMI (Body Mass Index) calculation is pretty simple. You divide the body mass (kg) by the square of the body height (m). The result is your BMI with the units of kg/m², resulting from mass in kilograms and height in metres.

Metric BMI Formula

BMI = kg / m²
(mass in kg divided by height in metres squared)

Imperial BMI Formula

BMI = (lbs x 703) / in²
(mass in lbs multiplied by 703 divided by height in inches squared)

What does BMI work out?

BMI helps to categorise your body mass into 4 commonly used ranges: Underweight (under 18.5), Normal weight (18.5 to 25), Overweight (25 to 30), and Obese (over 30).

The BMI calculation has its limitations, including if you are tall or have a higher than average muscle mass.

What are the limitations of BMI?

There are many limitations of BMI that stem from the fact that BMI is not an accurate measurement of health or fitness on an individual level. These include height and muscle mass.

Height: The BMI calculation states that a taller person is just a scaled up normal person, however, taller people tend to have slighter frames on average.

Muscle Mass: The BMI calculation does not differentiate between muscle mass or fat mass. A lean bodybuilder would be considered obese under BMI measurements.