What a Letter Means: a Short History of Ring Sizes

If you've ever tried to look up your ring size and ended up with three different answers, this article is for you.

Australia, and the United Kingdom, size rings by letters of the alphabet. Most of the world uses numbers. There's a reason — it's older than you'd think and slightly funnier than it should be.

The letter system came out of a British jewellery trade convention in the 1800s, when standards were being agreed for the first time. Before that, every ringmaker had their own measure: a Birmingham silversmith and a London goldsmith could make a ring labelled "size 4" and the rings would be a quarter-inch apart in actual diameter. This was, predictably, a problem. So the trade got together and agreed on a single graduated scale, with each step on the scale a fixed difference in millimetres. Someone, somewhere in the room, decided that letters would be more romantic than numbers. (I have a soft spot for whoever this person was.)

The American system that came along later used numbers because numbers were easier to put on a machine. Europe used millimetres because Europe used millimetres for everything. Japan adopted yet another system. The result is that a single ring, sitting in front of you, has at least three correct sizes. Your finger doesn't know about any of them. The ring doesn't know about any of them. Only the system knows.

Here is a short translation key, because you will at some point need it.

On the Australian scale, each letter is approximately 1.3 mm apart in inside diameter. A size L is roughly a US 6. A size N is about a US 7. P is about an 8. R is about a 9. T is about a 10. V is about an 11. X is about a 12. The pattern is roughly: one US size for every two Australian letters.

These are approximations. There are slight regional variations and at the half-letter level the conversion gets fuzzy. If you're ordering something one-of-a-kind, please don't rely on a chart — measure your finger properly, or have a jeweller do it for you.

There are several old, slow ways to measure at home. The most reliable is to take a ring that already fits the right finger and measure its inside diameter with a ruler that has millimetre markings. A size M is about 16.5 mm; a size R is about 17.7 mm; a size T is about 18.3 mm. Round to the nearest 0.1 mm and tell me what you measured. I'll do the rest.

The string-and-paper method is less accurate but useful if you have no ring to measure. Cut a thin strip of paper, wrap it around the base of the finger you want fitted, mark where the strip overlaps with a pen, and lay it flat against a ruler. Measure the length in millimetres. This is the circumference. The diameter is circumference divided by π (3.14). Take a photo of the strip and send it to me and I'll work it out.

Best of all, come to Paddington Markets on Saturday. I have a proper ring sizer with me every week. Sizing is free. It takes about a minute. The conversation is worth the trip in itself.

When you order from me, I'll always ask you for your size in whatever system you have it in. If you don't know it, tell me, and we'll work it out together. The letter doesn't matter. The fit does.