Imperial and metric
Common imperial sizes in mm:
1 inch = 25.4mm ≈ 25mm
3/4 inch = 19.05mm ≈ 19mm
1/2 inch = 12.5mm ≈ 13mm
1/4 inch = 6.35mm ≈ 6mm
1/8 inch = 3.17mm ≈ 3mm
Fasteners (bolts/nuts)
This table may be used to find the nearest matching bolt / nut sizes in either imperial or metric.
Sheet metal
https://en.wikipedia.org/wiki/Sheet_metal#Gauge
American Wire Gauge (AWG)
I’m not even going to attempt to explain:
https://en.wikipedia.org/wiki/American_wire_gauge#Tables_of_AWG_wire_sizes
Lumber sizes
2x4s are not actually 2 inches by 4 inches. When the board is first rough sawn from the log, it is a true 2×4, but the drying process and planing of the board reduce it to the finished size.
Shoe sizes (men)
AU SIZE |
UK SIZE |
EU SIZE |
US SIZE |
JAPAN |
FOOT LENGTH (MM) |
|---|---|---|---|---|---|
| 3 | 3 | 35.5 | 4 | 21.5 | 220 |
| 4 | 4 | 37 | 5 | 22.5 | 229 |
| 5 | 5 | 38 | 6 | 23.5 | 237 |
| 6 | 6 | 39 | 7 | 24.5 | 246 |
| 7 | 7 | 40.5 | 8 | 25.5 | 254 |
| 7.5 | 7.5 | 41 | 8.5 | 26 | 258 |
| 8 | 8 | 42 | 9 | 26.5 | 262 |
| 8.5 | 8.5 | 42.5 | 9.5 | 27 | 266 |
| 9 | 9 | 43 | 10 | 27.5 | 271 |
| 9.5 | 9.5 | 44 | 10.5 | 28 | 275 |
| 10 | 10 | 44.5 | 11 | 28.5 | 279 |
| 10.5 | 10.5 | 45 | 11.5 | 29 | 283 |
| 11 | 11 | 46 | 12 | 29.5 | 288 |
| 12 | 12 | 47 | 13 | 30.5 | 296 |
| 13 | 13 | 48 | 14 | 31.5 | 305 |
| 14 | 14 | 49.5 | 15 | 32.5 | 314 |