By dividing an adult’s weight in kilograms by their height in metres squared you will calculate their BMI For example, A BMI of 24 means 24kg/m2.
If you prefer to calculate using imperial units you would use the formula – Weight (lbs) / Height (inches)²] x 703
What is a healthy BMI?
For under 18s BMI calculations add additional variables to the formula such as gender and age.
If your BMI is:
- below 18.5 – you’re in the underweight range
- between 18.5 and 24.9 – you’re in the healthy weight range
- between 25 and 29.9 – you’re in the overweight range
- between 30 and 39.9 – you’re in the obese range
If you want to calculate your BMI, try the NHS healthy weight calculator.
How accurate is the BMI measurement?
A healthy BMI covers a range of measurements / figures, this range allows for naturally differing body shapes giving a healthy weight range for a specific height.
Clinicians may consider other variables when determining if you are a healthy weight or not.
Muscle is much denser therefore heavier than fat, so people who are particularly muscular, for example weight lifters, heavyweight boxers, and athletes, may be classified as obese due to their BMI measurement even if they are a healthy weight.
Your ethnic group May affect your risk of some health conditions. For example, adults of Asian origin may have a higher risk of health problems at BMI levels below 25.
If you’re pregnant do not use BMI as a measure. Contact your GP and / or midwife for advice if you would like advice on your weight.