Measuring the size bracelet you need is easy and requires very little equipment. If you buy a bracelet in a store, you can just try it on, but when ordering online it's very important to know what size bracelet to buy. If you don't want to measure yourself, you can also go to a local jewelry store and ask to have your wrists sized. Part of your correct bracelet size is personal preference, whether you like your bracelets to fit loosely or tightly.
Locate a flexible tape measure, such as one used by sewers or knitters. A stiff metal one will not be nearly as accurate for this type of measurement.
Wrap the tape measure around your wrist just above the wrist bone. Above your wrist bone is the side closer to your elbow.
Add anywhere from 1/4 to 1 inch to the measurement you read off the tape measure. How much extra to add depends on how close fitting you like your bracelets. About 1/2 inch is average.