18 inch (DN 450) pipe dimensions & weight
18 inch (DN 450) steel pipe has an outside diameter of 457.0 mm (17.992 in) in every schedule. Below: wall thickness, inside diameter, weight per metre and water capacity for each ASME B36.10M / B36.19M schedule.
| Schedule | Wall (mm) | Wall (in) | ID (mm) | CS kg/m | CS lb/ft | SS 304 kg/m | Water L/m |
|---|---|---|---|---|---|---|---|
| Sch 5S | 4.19 | 0.165 | 448.62 | 46.79 | 31.44 | 47.27 | 158.07 |
| Sch 10S | 4.78 | 0.188 | 447.44 | 53.31 | 35.82 | 53.85 | 157.24 |
| Sch 10 | 6.35 | 0.250 | 444.30 | 70.57 | 47.42 | 71.29 | 155.04 |
| Sch 20 | 7.92 | 0.312 | 441.16 | 87.71 | 58.94 | 88.60 | 152.86 |
| Sch 30 | 11.13 | 0.438 | 434.74 | 122.38 | 82.24 | 123.63 | 148.44 |
| STD | 9.53 | 0.375 | 437.94 | 105.16 | 70.67 | 106.23 | 150.63 |
| Sch 40 | 14.27 | 0.562 | 428.46 | 155.80 | 104.70 | 157.39 | 144.18 |
| Sch 60 | 19.05 | 0.750 | 418.90 | 205.74 | 138.26 | 207.84 | 137.82 |
| XS | 12.70 | 0.500 | 431.60 | 139.15 | 93.51 | 140.57 | 146.30 |
| Sch 80 | 23.83 | 0.938 | 409.34 | 254.55 | 171.06 | 257.14 | 131.60 |
| Sch 100 | 29.36 | 1.156 | 398.28 | 309.62 | 208.06 | 312.78 | 124.59 |
| Sch 120 | 34.93 | 1.375 | 387.14 | 363.56 | 244.31 | 367.27 | 117.71 |
| Sch 140 | 39.67 | 1.562 | 377.66 | 408.26 | 274.35 | 412.42 | 112.02 |
| Sch 160 | 45.24 | 1.781 | 366.52 | 459.37 | 308.70 | 464.05 | 105.51 |
CS = carbon steel (7.85 g/cm³). SS 304 at 7.93 g/cm³; for 316 multiply CS weight by 1.017. Water capacity = internal volume per metre.
Matching 18" flanges and fittings
| Class 150 flange | OD 635 mm · thk 38.1 mm · PCD 577.9 mm · 16 × 1-1/8" bolts |
| Class 300 flange | OD 710 mm · thk 58.8 mm · PCD 628.6 mm · 24 × 1-1/4" bolts |
| B16.9 fittings | 90° LR 686 mm · 45° LR 286 mm · 90° SR 457 mm · tee 343 mm · reducer 381 mm · cap 203 mm |
Full tables: Class 150 · Class 300 · B16.9 fittings.
Frequently asked questions
What is the OD of 18 inch pipe?
18 inch (DN 450) pipe has an outside diameter of 457.0 mm (17.992 in), regardless of schedule.
What is the wall thickness of 18 inch Schedule 40 pipe?
14.27 mm (0.562 in), giving an inside diameter of 428.46 mm.
How much does 18 inch Schedule 40 pipe weigh?
About 155.80 kg/m (104.70 lb/ft) in carbon steel, or 934.8 kg for a 6 m length.
What is the wall thickness of 18 inch Schedule 80 pipe?
23.83 mm, with an inside diameter of 409.34 mm and weight of 254.55 kg/m.
Last updated 2026-11-02