BMI Calculator
Enter your details below to see your BMI result and whether it falls into the underweight, healthy, overweight or obese range. This calculator is intended for general guidance and awareness only.
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How the BMI Calculator Works
The calculator uses:
Example 1: A Standard Calculation
If a person is 1.75m (5ft 9in) tall and weighs 70kg (154 lbs):
– The calculator divides the weight by the height squared (70 ÷ 1.75²).
This results in a BMI of 22.9, which places them in the ‘Healthy weight’ category.
Example 2: The Athlete Exception (Why BMI isn’t perfect)
If a professional rugby player is 1.80m tall and weighs 105kg due to heavy muscle mass:
– The calculator will return a BMI of 32.4, which technically falls into the ‘Obese’ category.
Takeaway: Because muscle is much denser than fat, BMI often overestimates health risks in highly muscular athletes, which is why it should only be used as a general baseline.
What Is Body Mass Index (BMI)?
For more detailed guidance on healthy weight, visit the official NHS website.
When Should You Use a BMI Calculator?
About This BMI Calculator
BMI is a general screening tool only and does not diagnose health conditions. Individual health assessments should always be discussed with a qualified professional.
Frequently Asked Questions
Your BMI result places you into a general category such as underweight, healthy, overweight or obese based on standard ranges.
BMI is a useful, high-level screening tool, but it is not a diagnostic measure of health. It only calculates mass, meaning it cannot distinguish between fat, muscle, or bone density. It also does not account for age, gender, or how fat is distributed around the body.
Yes. You can choose either metric or imperial units when entering your height and weight.
Yes. All calculators on Calchub are free to use. You’re welcome to bookmark any of your favourites and use them as much as you would like.
No. If your BMI result places you outside the healthy range, it should simply serve as a prompt to have a conversation with your GP or a qualified healthcare provider. They will use more comprehensive tests (like blood pressure, cholesterol checks, or body fat calipers) to assess your actual health.
Disclaimer
Last checked/updated February 2026.