# BMI Calculator

Calculate your Body Mass Index — a screening measure based on height and weight.

Body Mass Index, or BMI, is a simple screening calculation based on height and weight. It is commonly used to group adult body weight into broad categories.

## How do you calculate BMI?

 **Metric:** BMI = weight in kilograms ÷ height in metres².

 **Imperial:** BMI = (weight in pounds × 703) ÷ height in inches².

## Adult BMI categories

 Coach Plum uses the standard adult category boundaries: Underweight below 18.5, Normal from 18.5 to below 25, Overweight from 25 to below 30, and Obese at 30 or above.

## What are the limitations of BMI?

 BMI does not distinguish fat mass from muscle mass and does not describe where body fat is stored. A muscular person can therefore have a high BMI without having the same body composition as another person with the same BMI.

 BMI is best treated as one screening measure rather than a complete description of health or fitness. If you provide body-fat percentage, Coach Plum also shows estimated lean mass, fat mass, FFMI and FMI to add more context.

## When does Coach Plum show health guidance?

 If BMI is below 18.5, the results page shows an NHS-based Health Guidance notice. The calculation remains visible; the notice adds context rather than blocking the result.

[HTML page](https://coachplum.com/bmi/calculator)