Body Mass Index (BMI) Calculator

Body Mass Index (BMI) Calculator (Metric & Imperial) — with Worked Example

Use this BMI calculator to estimate your Body Mass Index from height and weight. It will also show the formula and the steps used (including any unit conversions).

How to use: choose Metric (kg/cm) or Imperial (lb/ft/in), enter your details, then press “Calculate BMI”.

Units

Metric (kg, cm) Imperial (lb, ft/in)

Weight (kg)

Height (cm)

Weight (lb)

Height (ft / in)

Feet

Inches

Enter your height and weight, then calculate your BMI. For adults only.

How the maths works

BMI categories (adults)

• Underweight: less than 18.5
• Normal weight: 18.5 to 24.9
• Overweight: 25 to 29.9
• Obesity: 30 or higher

Medical disclaimer: This BMI calculator provides an estimate for general information only. BMI does not directly measure body fat and can be misleading for athletes, older adults, pregnant people, and some ethnic groups. It is not a diagnosis. If you’re concerned about your weight or health, speak to a qualified healthcare professional.

What is BMI?

Body Mass Index (BMI) is calculated from weight and height. It’s often used as a simple screening measure for underweight, healthy weight, overweight, and obesity in adults. For health decisions, BMI should be considered alongside waist size, lifestyle, medical history, and professional assessment.