Bangles that need to be slipped over the hand (i.e. the ones that do not have closures), are measured in a particular way to see if they fit the hand. They are measured by their diameter, which is basically the measure of the length of a straight line passing through the center of the bangle. The unit of measurement in this case is inches.
Now, an inch is further divided into 16 sections. So, when we say that a bangle size is 2-8 (pronounced two-eight), it means the diameter of the bangle is 2 full inches plus 8 sections of the total 16 sections of the inch. This effectively converts to 2inches + 8/16 inches, which is 2 inches plus half an inch. In other words this size will be 2.5" (pronounced two point five inches).
There are few ways in which it can be ascertained if the bangle is a right fit.
Take an existing bangle and measure the diameter (inside) and then compare with the measurement chart given below or with the measurement in the actual bangle listing. The inside diameter of a bangle is the most accurate way to measure a bangle.
As long as you measure the inside diameter of your current bangles this will be an accurate way to find your bangle size.