BMICALCULATOR
Check your body mass index using NHS weight categories. Works with metric or imperial measurements.
BMI
What is BMI?
Body mass index is a number calculated from your height and weight. The NHS uses it as a quick way to screen whether your weight might be putting your health at risk. It's not a diagnostic tool — it won't tell you your body fat percentage or how fit you are — but it gives a rough starting point. BMI was designed for population-level statistics in the 1800s, and while it's still widely used, most doctors will consider it alongside other measurements. If your BMI is outside the healthy range, your GP might also check your waist circumference, blood pressure, and cholesterol before drawing any conclusions.
How the calculation works
The formula itself is straightforward. You divide your weight in kilograms by your height in metres squared. A person who is 1.75m tall and weighs 72kg has a BMI of 23.5, which falls in the NHS healthy range.
Enter your height
Use centimetres if you think metric, or feet and inches if you're used to imperial. Most people in the UK know their height in feet and inches.
Enter your weight
Use kilograms or stone and pounds. If you only know your weight in pounds, divide by 14 to get stone — or just use the metric option.
Read your result
Your BMI number appears with the NHS category. The colour-coded scale shows where you sit relative to the standard ranges.
BMI Formula
If using imperial measurements, the calculator converts feet and inches to metres (1 inch = 0.0254m) and stone and pounds to kilograms (1 lb = 0.4536kg) before applying the formula. The NHS uses the same formula for all adults over 18.
Tips & Best Practices
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BMI doesn't distinguish between muscle and fat. If you train with weights regularly, your BMI may overstate your health risk.
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The NHS says waist circumference matters too. For men, a waist over 94cm increases health risks. For women, it's 80cm.
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For people of South Asian, Chinese, or other Asian ethnic backgrounds, the NHS suggests health risks may increase at a lower BMI (23 rather than 25).
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BMI categories don't apply to children or teenagers. The NHS has a separate healthy weight calculator for under-18s.
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If you're concerned about your weight, your GP can give personalised advice that goes well beyond a single number.
Frequently Asked Questions
Mandeep Singh · 25+ Years UK Financial Services
Important Information
This calculator is for informational purposes only and does not constitute financial advice or a personal recommendation.
Results are estimates based on the information you provide and may not reflect your actual financial position.
You should consider seeking independent professional advice tailored to your specific circumstances before making any financial decision.