BMI Calculator

As a registered nutritionist, I use BMI (Body Mass Index) as one starting point among several when thinking about a client’s weight and health — never in isolation. Use the calculator below to check your BMI in either metric or imperial units.

How This Is Calculated

BMI is calculated by dividing your weight in kilograms by the square of your height in metres (BMI = weight (kg) ÷ height (m)²). If you enter pounds or inches, the calculator converts these to kilograms and centimetres first.

Your result is then placed into one of four standard categories: under 18.5 (underweight), 18.5–24.9 (healthy weight), 25–29.9 (overweight), or 30 and above (obese). If you tick the ethnicity option, the calculator also shows your category using NICE’s lower thresholds (23 for overweight, 27.5 for obesity) for South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean adults, who are known to reach increased health risk at a lower BMI than the general population. This is educational information, not a personal medical assessment.

Related Reading

If you are of South Asian heritage, you may find my article on rice, roti and diabetes risk under NICE’s BMI guidance particularly useful — it looks at how these lower BMI thresholds relate to everyday food choices and type 2 diabetes risk. For broader support, see my weight loss nutrition page, or my diabetes nutrition page if your BMI result relates to a diabetes risk or diagnosis you have been given.

Frequently Asked Questions

This calculator provides general information only and is not medical advice. It is not a substitute for individual clinical assessment. Please speak to your GP or a registered dietitian about any concerns regarding your weight or health.