We recommend taking a soft tape measure (the type that you would use for sewing) and wrap it around your wrist. If you don't have a tape measure, then just cut a long strip of paper or a piece of string / cord, wrap it around your wrist, mark it, and compare this measurement with a flat ruler.
Make sure to measure the wrist you intend to wear the bracelet on, as some people have different measurements for their left and right wrist.
This accommodates the materials that the bracelet is made out of. Chunkier bracelet styles will need a greater allowance, and so do bracelets that have a wider strap. Each page in the shop has guidance on how to get the right fit.
Also keep in mind how you would like your bracelet to fit. If you prefer a looser style, err on the generous side.
Our general recommendation is to add approx 1/2 an inch to your wrist measurement. But please keep in mind any advice on specific product pages. We always recommend that you round up, instead of down, if you have to make a choice.