Measure your wrist carefully (use a flexible measuring tape or string + ruler). A typical rule: the bracelet should be comfortable — not too tight or loose. A good guideline: you should be able to slide one finger between bracelet and wrist. If unsure, size up slightly. https://www.tumblr.com/divourdiamonds/801276270803566592/how-to-choose-the-perfect-tennis-bracelet-for?source=share