An ill-fitting ring can be quite irritating. Part of making sure that your ring fits you correctly is knowing your ring size. This can be difficult when you travel to other countries and you aren't familiar with how to convert American ring sizes to the sizes in other countries. While we use numbers in the US to indicate ring sizes, in the UK they use letters and half steps (such as G and G 1/2). There's a simple trick that you can do to help convert between American and British ring sizes.
Convert the smallest American ring size, size 1/2, to the smallest British ring size, size A. Approximately each US half size larger converts to a new UK letter size. For example, a US size 1 is a British B. Size 1 1/2 is a British size C. An American size 2 is a British size D. However, this changes at American size 4 3/4. This size equals a British J. From this point on each half size bigger is a new letter in the British system. For example an American size 5 1/4 is a British K. A size 5 3/4 is a British L.
Convert all American sizes that end in 1/4 or 3/4 up a British half size, for American sizes 1/2 to 4 1/2. For example, American size 3 is a British F. Thus American size 3 1/4 equals F 1/2. American size 3 1/2 is a British size G and American size 3 3/4 is equal to the UK's size G 1/2. This changes at size 4 3/4, which equals J and size 5 equals J 1/2. From that point on, as the Americans sizes get larger by 1/4; the corresponding British sizes increase by 1/2. For example, size 5 1/4 equals K and size 5 1/2 equals K 1/2.
Try on the ring if possible when shopping. Because America has more ring sizes than the UK, you're not always going to get an exact match for your ring size. You'll have to decide if you want something a tiny bit smaller or a tiny bit larger.
The typical ring size for a US woman is between a size 6 and 8, or L and Q in the UK. The average ring size for a man is between 9 and 11, or J and W.