BWG & SWG gauge to mm chart
Heat exchanger and condenser tube walls are specified in BWG; wire and thin sheet often in SWG. A higher gauge number means a thinner wall.
BWG — Birmingham wire gauge (tubes)
| BWG | mm | inch |
|---|---|---|
| 0000 | 11.53 | 0.454 |
| 000 | 10.80 | 0.425 |
| 00 | 9.65 | 0.380 |
| 0 | 8.64 | 0.340 |
| 1 | 7.62 | 0.300 |
| 2 | 7.21 | 0.284 |
| 3 | 6.58 | 0.259 |
| 4 | 6.05 | 0.238 |
| 5 | 5.59 | 0.220 |
| 6 | 5.16 | 0.203 |
| 7 | 4.57 | 0.180 |
| 8 | 4.19 | 0.165 |
| 9 | 3.76 | 0.148 |
| 10 | 3.40 | 0.134 |
| 11 | 3.05 | 0.120 |
| 12 | 2.77 | 0.109 |
| 13 | 2.41 | 0.095 |
| 14 | 2.11 | 0.083 |
| 15 | 1.83 | 0.072 |
| 16 | 1.65 | 0.065 |
| 17 | 1.47 | 0.058 |
| 18 | 1.24 | 0.049 |
| 19 | 1.07 | 0.042 |
| 20 | 0.89 | 0.035 |
| 21 | 0.81 | 0.032 |
| 22 | 0.71 | 0.028 |
| 23 | 0.64 | 0.025 |
| 24 | 0.56 | 0.022 |
| 25 | 0.51 | 0.020 |
| 26 | 0.46 | 0.018 |
SWG — Standard (Imperial) wire gauge
| SWG | mm | inch |
|---|---|---|
| 7/0 | 12.700 | 0.5000 |
| 6/0 | 11.786 | 0.4640 |
| 5/0 | 10.973 | 0.4320 |
| 4/0 | 10.160 | 0.4000 |
| 3/0 | 9.449 | 0.3720 |
| 2/0 | 8.839 | 0.3480 |
| 0 | 8.230 | 0.3240 |
| 1 | 7.620 | 0.3000 |
| 2 | 7.010 | 0.2760 |
| 3 | 6.401 | 0.2520 |
| 4 | 5.893 | 0.2320 |
| 5 | 5.385 | 0.2120 |
| 6 | 4.877 | 0.1920 |
| 7 | 4.470 | 0.1760 |
| 8 | 4.064 | 0.1600 |
| 9 | 3.658 | 0.1440 |
| 10 | 3.251 | 0.1280 |
| 11 | 2.946 | 0.1160 |
| 12 | 2.642 | 0.1040 |
| 13 | 2.337 | 0.0920 |
| 14 | 2.032 | 0.0800 |
| 15 | 1.829 | 0.0720 |
| 16 | 1.626 | 0.0640 |
| 17 | 1.422 | 0.0560 |
| 18 | 1.219 | 0.0480 |
| 19 | 1.016 | 0.0400 |
| 20 | 0.914 | 0.0360 |
| 21 | 0.813 | 0.0320 |
| 22 | 0.711 | 0.0280 |
| 23 | 0.610 | 0.0240 |
| 24 | 0.559 | 0.0220 |
| 25 | 0.508 | 0.0200 |
| 26 | 0.457 | 0.0180 |
Frequently asked questions
What is 16 BWG in mm?
1.65 mm (0.065 in).
What is 18 SWG in mm?
1.219 mm.
Which gauge is used for heat exchanger tubes?
BWG — for example 3/4 in OD × 16 BWG or 1 in OD × 14 BWG tubes.
Last updated 2026-11-02