Have you ever fallen in love with a bespoke ring whilst browsing the internet or scrolling through social media, but don't know whether it will fit as you don't know your ring size? The best method would be to buy a cheap ring and send it to me. This will then be returned with your order. If you are buying from a different country, you may find this ring conversion helpful.
Another way to get an accurate ring size is to go to at least two jewellers and ask them to measure your finger. You should get two jewellers confirm your ring size as there are many ring mandrels and ring sizers and which may be calibrated slightly differently - even 1mm will make a different in sizing rings. Most jewellers will use a Wheatsheaf mandrel and ring sizer, which is what I use.
Or you can buy a plastic ring sizer online and take a measurement from that - if you are buying a flexible sizer remember to tighten it to what looks roughly the right size then place the sizer on your finger, starting from the tip and move it down, rather than closing it from the base. Make adjustments as necessary so it's not too loose / tight and move it up and down your finger. This is because the ring will need to get over your knuckle, and for many people this will be bigger than the base of your finger.
Methods such as tying string around your finger and trying to match it to a print out ring sizer will not give you accurate results and you should avoid this.
A ring that is 6mm wide or more will need to be approximately 1/2 to 1 size bigger - this is because it needs to take the fleshy part of your finger into account, so a little bigger will be more comfortable. You can ask a jewellery to measure with a wider ring sizer so it's accurate.
Make sure you measure your finger at different times of the day as fingers may be a different size in the morning to what it is in the evening. For some people, fingers will also usually be bigger in summer when the weather is hot rather than winter where the fleshy part may contract.