Chains
Use a soft measuring tape or a length of string around your neck. Adjust it until it sits where you want the chain to fall, then measure that length. Compare it with the measurements listed on the product.
Bracelets
Measure around your wrist where you wear your bracelet. Allow space for comfortable movement. Check the individual product measurements before ordering.
Earrings
Check the face dimensions on the product listing. A ruler can help you picture how the earrings will look on your ear.