BMI Calculator
Find out your Body Mass Index and what it means for your health.
How this BMI calculator works
Body Mass Index is calculated by dividing your weight in kilograms by the square of your height in metres: BMI = weight (kg) ÷ height² (m²). The World Health Organization classifies adults into four main categories based on this number.
What the result means
A healthy BMI (18.5–24.9) suggests your weight is proportionate to your height. However, BMI is a blunt instrument — it cannot distinguish between muscle and fat. A competitive weightlifter may show as 'overweight' while carrying very little body fat. Always interpret BMI alongside other health indicators such as waist-to-height ratio and body fat percentage.
If your BMI is outside the healthy range, it's worth speaking with your GP before making major dietary or exercise changes. This calculator provides general information only and is not a substitute for medical advice.
Frequently Asked Questions
- What is BMI?
- Body Mass Index (BMI) is a measure of body fat based on height and weight. It applies to adult men and women and is calculated as weight (kg) divided by height (m) squared.
- What is a healthy BMI?
- According to the World Health Organization, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese.
- Is BMI accurate?
- BMI is a useful screening tool but has limitations. It doesn't directly measure body fat, so a muscular athlete may have a high BMI without excess fat. Use it alongside other measures like waist circumference and body fat percentage.
- Does BMI differ for different ethnicities?
- Yes. Research suggests that people of South Asian, Chinese, and other East Asian descent may be at higher health risk at lower BMI thresholds. Some guidelines use 23 as the 'overweight' cutoff for these groups rather than 25.