Welcome to our free BMI Calculator designed for UK users. Quickly check your Body Mass Index using kilograms and centimetres, or stones and pounds. This tool helps you understand whether your weight falls within a healthy range according to standard NHS guidelines.
How to Use This BMI Calculator
- Select your preferred units (Metric: kg + cm or Imperial: stones/pounds + feet/inches).
- Enter your height.
- Enter your weight.
- Click Calculate to see your BMI score and category.
BMI Formula Used
Our calculator uses the standard Body Mass Index formula recognised worldwide and by the NHS:
BMI = weight (kg) ÷ [height (m)]²
For imperial measurements, the calculator automatically converts stones/pounds and feet/inches into metric units before applying the formula.
BMI Categories (Adults)
- Below 18.5 – Underweight
- 18.5 – 24.9 – Healthy weight
- 25 – 29.9 – Overweight
- 30 and above – Obese
These ranges are based on World Health Organization and NHS guidelines for adults. Results may differ slightly for athletes, older adults, or pregnant women.
Worked Example
Example: A person who is 5 feet 9 inches (175 cm) tall and weighs 12 stone 7 pounds (79.4 kg).
- Height in metres: 1.75 m
- BMI calculation: 79.4 ÷ (1.75 × 1.75) = 25.9
- Category: Overweight
You can also use our Percentage Calculator to track weight-loss progress as a percentage over time.
Why BMI Matters
BMI is a simple screening tool that gives a general indication of whether your weight is healthy for your height. It is widely used by GPs and health professionals in the UK. However, it does not directly measure body fat and may not be accurate for people with high muscle mass.
For more detailed health guidance, visit the official NHS BMI Calculator page.
Limitations of BMI
- Does not distinguish between muscle and fat.
- May classify muscular athletes as overweight or obese.
- Less accurate for older adults and some ethnic groups.
- Not suitable for children, pregnant women, or those under 18 without specialist guidance.
If you are concerned about your weight or health, speak to your GP. You can also explore our Scientific Calculator for other precise calculations.
Frequently Asked Questions
Is this BMI calculator accurate for UK users?
Yes. It uses the same standard formula recommended by the NHS and World Health Organization. You can switch between metric and imperial units commonly used in the UK.
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered healthy. Scores outside this range may indicate increased health risks.
Can I use this calculator if I measure in stones and pounds?
Yes. Simply select the imperial option and enter your height in feet/inches and weight in stones and pounds. The calculator converts everything automatically.
Should I only rely on BMI?
No. BMI is a useful starting point but should be considered alongside waist circumference, lifestyle, and advice from a healthcare professional. For official guidance, see the NHS Healthy Weight pages.
Disclaimer: This BMI calculator is for general informational purposes only and does not provide medical advice. Results should not replace professional medical assessment. Always consult a qualified healthcare professional for personalised advice. See our full Disclaimer page.
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