Definition: BMI stands for Body Mass Index. The BMI can be defined as: - BMI = weight in kilograms / height in meters squared - BMI > 30 means it's considered to be overweight and - BMI < 18.5 or 24 - 26 is considered to be underweight This is the scale used by the UK Government for determining whether someone needs to purchase life insurance. BMI Chart Life Insurance (BCLI) allows you to compare different insurers' BCI values without actually buying any life insurance policies from them as they can compare their own BCI with yours in real time.