My parents were traveling a few years back and I asked them to bring me back a white gold chain for a charm that I had (the original chain broke). I knew where the old chain used to sit, but I couldn't remember what length. So I used a tape measure to figure out where I wanted it to be. When they brought the chain back from their trip, it wasn't what I wanted. Had I had a chart like this, it would have been so helpful. This picture does wonders for necklace shopping.