Pipes and Tubes - Imperial vs. Metric Sizes
SI vs. Imperial pipe sizes.
The United States is the only major industrial country where inch sizes are commonly used.
| Nominal Imperial Pipe Size (NPS) | Nominal Metric Pipe Size (DN) | ASHRAE (mm) | AWWA (mm) | NFPA (mm) | ASTM copper tube (mm) |
|---|---|---|---|---|---|
| 1/8 | 6 | 6 | |||
| 3/16 | 8 | 8 | |||
| 1/4 | 10 | 8 | 10 | ||
| 3/8 | 12 | 10 | 12 | ||
| 1/2 | 15 | 15 | 12.7, 13 | 12 | 15 |
| 5/8 | 18 | 18 | |||
| 3/4 | 20 | 20 | 22 | ||
| 1 | 25 | 25 | 25 | 25, 25.4 | 28 |
| 1 1/4 | 32 | 32 | 33 | 35 | |
| 1 1/2 | 40 | 40 | 45 | 38, 38.1 | 42 |
| 2 | 50 | 50 | 50, 50.8 | 51 | 54 |
| 2 1/2 | 65 | 65 | 63, 63.5 | 63.5, 64 | 67 |
| 3 | 80 | 80 | 75 | 76, 80 | 79 |
| 3 1/2 | 90 | 89 | |||
| 4 | 100 | 100 | 100 | 102 | 105 |
| 4 1/2 | 115 | 114.3 | |||
| 5 | 125 | 127 | 130 | ||
| 6 | 150 | 150 | 150 | 152 | 156 |
| 8 | 200 | 200 | 200 | 103 | 206 |
| 10 | 250 | 250 | 250 | 257 | |
| 12 | 300 | 300 | 300 | 305 | 308 |
| 14 | 350 | 350 | |||
| 16 | 400 | 400 | |||
| 18 | 450 | ||||
| 20 | 500 | 500 | |||
| 24 | 600 | 600 | |||
| 28 | 700 | ||||
| 30 | 750 | ||||
| 32 | 800 | ||||
| 36 | 900 | ||||
| 40 | 1000 | ||||
| 44 | 1100 | ||||
| 48 | 1200 | ||||
| 52 | 1300 | ||||
| 56 | 1400 | ||||
| 60 | 1500 |
