So I decided it would be nice and handy if I had a little table which told me which gauge I wanted when considering ordering from American Jewellery shops, and me being the considerate bloke I am I though I'd chuck it on my web page since if I want to know, it's more than likely that someone else will want to know!
I should also add that I've rounded sizes to the nearest 1
decimal place since that's all the European shops list their
sizes to, and I for one am pretty sure I couldn't see the
difference between 1.19mm and 1.2mm with the naked eye,
however I do know that you can feel the difference between 1.6mm
and 2.0mm!

I've converted both ways using the standard sizes offered by most companies
whose web sites I visited, just for convenience!
| Gauge | Millimetres |
|---|---|
| 20 | 0.8 |
| 18 | 1.0 |
| 16 | 1.2 |
| 14 | 1.6 |
| 12 | 2.4 |
| 8 | 3.2 |
| 6 | 4.0 |
| 4 | 4.8 |
| 2 | 6.4 |
| 0 | 8.0 |
| Millimetres | Gauge |
|---|---|
| 1 | 18 |
| 1.2 | 16 |
| 1.6 | 14 |
| 2.0 | 13? |
| 2.4 | 12 |
| 3.2 | 8 |
| 4.0 | 6 |
| 5.0 | 3? |
| 6.0 | 3? |
| 8.0 | 0 |