Making sure you get the ring size right is very important, I happy to post you a free plastic ring gauge if that helps. However, most high street jewellers are generally happy to check your size for free.
Wider rings will need to be slightly larger in circumference than narrow ones, if possible use a sizing gauge in a similar width to the ring you're ordering.
In the UK an A-Z scale gauge is used (the same as in Australia), but there are several systems used in the rest of the world. Here's an international ring size conversion with internal ring circumferences to help.
Ideally a ring will fit comfortably over the knuckle but there will be a little resistance when taking it off. The size of your finger is likely to change a little depending on the weather, time of day etc. Ideally you should have you size checked a couple of times at different times of day.
Please contact me if you have any questions about finding out your ring size.
Chain lengths are usually 40, 45 or 50cm long but I can get a chain made to any length. Small extender chains can be fitted to necklaces to make them adjustable.