BiologyHuman Health and DiseaseGCSE

Body Mass Index (BMI) Calculator

A calculation used to estimate body fat and determine if a person's weight is within a healthy range relative to their height.

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Body Mass Index

Formula first

Overview

BMI acts as a screening tool to identify potential weight-related health risks, such as being underweight, overweight, or obese. It is calculated by dividing an individual's weight in kilograms by the square of their height in meters. While widely used, it does not account for muscle mass or fat distribution, making it an estimate rather than a direct measurement of body fat percentage.

Symbols

Variables

Mass = Mass (kg), Height = Height (m), BMI = Body Mass Index

Mass
Mass (kg)
kg
Height
Height (m)
BMI
Body Mass Index

Apply it well

When To Use

When to use: Apply this when assessing an individual's general weight category based on clinical guidelines.

Why it matters: Maintaining a healthy BMI is linked to a reduced risk of cardiovascular diseases, type 2 diabetes, and certain cancers.

Avoid these traps

Common Mistakes

  • Forgetting to convert height from centimeters to meters.
  • Multiplying the height by 2 instead of squaring it.

One free problem

Practice Problem

Calculate the BMI of a person who weighs 60kg and is 1.5m tall.

Mass (kg)60 kg
Height (m)1.5 m

Solve for: BMI

Hint: Square 1.5 first, then divide 60 by the result.

The full worked solution stays in the interactive walkthrough.

References

Sources

  1. NHS (National Health Service), 'What is the body mass index (BMI)?'
  2. World Health Organization (WHO) BMI Classification
  3. World Health Organization (WHO) BMI classification standards
  4. AQA GCSE Biology Specification
  5. AQA/Edexcel GCSE Biology Specification: Health, disease and the development of medicines.