How do I know what length chain to buy?
    If you don't already have a chain or necklace of the right length that you can measure, then use a length of string or wool to wrap round your neck down to the point to which you want the chain to fall.

If you are using the chain to hang a pendant, consider first where you want to postion the pendant.
Thread the string or wool through the pendant bale and position it, using the string around your neck, where you want to wear it. Measure the length of the string and this is the chain length to buy.