Work Out Your BMI with Our Free Body Mass Index Calculator
Our BMI calculator helps you determine whether your weight falls within a healthy range for your height, using the standard measurement recognised by the NHS.
How to use: BMI Calculator UK | Calculate Your Body Mass Index
Body Mass Index, or BMI, is a straightforward measurement that uses your height and weight to assess whether you're at a healthy weight. The calculator divides your weight in kilograms by your height in metres, squared. For example, if you weigh 70kg and you're 1.75 metres tall, you'd divide 70 by (1.75 × 1.75), which equals 70 ÷ 3.06, giving you a BMI of approximately 23. The NHS uses standard BMI categories: underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (30 and above). Whilst BMI is a useful screening tool, it doesn't account for muscle mass, bone density, or overall fitness levels, so it's best used alongside other health indicators.
Consider a 45-year-old man from Manchester weighing 85kg at 1.80 metres tall—his BMI would be 26.2, placing him in the overweight category. Similarly, a woman in Bristol weighing 65kg at 1.65 metres would have a BMI of 23.9, sitting comfortably within the normal range. Another example: a rugby player from Wales might weigh 100kg at 1.85 metres, giving a BMI of 29.2, technically overweight, yet possess significant muscle mass. These examples highlight why discussing results with your GP is sensible, particularly if you're very muscular or have existing health conditions. Your doctor can provide personalised guidance beyond the numbers.
When using our calculator, ensure you're measuring your height accurately without shoes, and weigh yourself on reliable scales, ideally in the morning. Don't rely solely on BMI if you're very fit or athletic—muscle weighs more than fat. Check your result regularly, perhaps monthly, to track trends rather than fixating on single measurements. If your BMI indicates you're overweight or obese, consult your GP before starting any weight loss programme. They can rule out underlying health issues and recommend appropriate diet and exercise plans suited to your circumstances.