This is one of the most common questions I receive from online customers, most people know their ring size but unless they already have a bangle they can measure they don't know how to find their bangle measurement.
Measuring a bangle
If you already have a bangle that you are happy fits you well, you can just measure the widest part of the bangle, the diameter. It doesn't matter if it is in inches, cm, or mm. The measurement should be the inner width.
Measuring your hand
If you need to measure your hand for your bangle size the easiest way is to make a fist, measure from the middle of the index (first finger) knuckle to the middle of the little (last finger) knuckle. Again it doesn't matter if that is in inches, cm or mm.
Remember it is better to be a slight bit too large than too small!