If you have a bangle that fits, measure the inside diameter.
If you don’t have a bangle to try on, you can measure your hand. Measure your hand when closed as if you were putting on a bangle, keeping your thumb tucked in. This is the important measurement, as the bangle must go over the knuckles.
My wife and daughters’ hands vary in size, my wife's circumference is 24cm and my daughter's circumference is 22cm. Both my wife and daughter wear size medium bangles.
As everyone’s hands are different it is not an exact science and only a gauge.
If you are unsure, please contact me and we can help decide on the size of your bangle?