Schedule 40 vs Schedule 160 Pipe
The default wall against the heaviest numbered schedule — how much metal Schedule 160 adds, how much bore it takes away, and where that trade is worth making.
- Sizes with both
- 19
- Weight penalty
- +134% on average
- Flow area lost
- -30% on average
- Schedule 160 starts at
- NPS 1/2
Short answer. Schedule 160 is the heaviest numbered schedule B36.10M publishes. Against Schedule 40 it roughly doubles the wall in small bore — averaging +134% weight and 30% less flow area across the 19 sizes that publish both. It is a high-pressure and severe-service wall, not a general upgrade.
Two schedules at opposite ends of the series
At NPS 2 the Schedule 40 wall is 0.154 in (3.9 mm) and the Schedule 160 wall is 0.344 in (8.7 mm) — 2.2 times the metal. The bore closes from 2.067 in (52.5 mm) to 1.687 in (42.8 mm), so a line sized on Schedule 40 flow will not deliver the same duty in Schedule 160 without moving up in NPS.
That is the practical trap: swapping schedule for pressure capacity is also a hydraulic change. On long runs the extra pressure drop can exceed the margin the heavier wall was bought for.
Dimensions are given in inches, with the millimetre equivalent beneath in grey.
| NPS | OD | Sch 40 wall | Sch 160 wall | Sch 40 bore | Sch 160 bore | Sch 40 weight | Sch 160 weight | Weight change | Flow area change |
|---|---|---|---|---|---|---|---|---|---|
| NPS 1/2 | 0.84021.34 mm | 0.1092.77 mm | 0.1884.78 mm | 0.62215.80 mm | 0.46411.79 mm | 0.851.27 kg/m | 1.311.95 kg/m | +54% | -44% |
| NPS 3/4 | 1.05026.67 mm | 0.1132.87 mm | 0.2195.56 mm | 0.82420.93 mm | 0.61215.54 mm | 1.131.68 kg/m | 1.942.89 kg/m | +72% | -45% |
| NPS 1 | 1.31533.40 mm | 0.1333.38 mm | 0.2506.35 mm | 1.04926.64 mm | 0.81520.70 mm | 1.682.50 kg/m | 2.844.23 kg/m | +69% | -40% |
| NPS 1 1/4 | 1.66042.16 mm | 0.1403.56 mm | 0.2506.35 mm | 1.38035.05 mm | 1.16029.46 mm | 2.273.38 kg/m | 3.765.60 kg/m | +66% | -29% |
| NPS 1 1/2 | 1.90048.26 mm | 0.1453.68 mm | 0.2817.14 mm | 1.61040.89 mm | 1.33833.99 mm | 2.724.04 kg/m | 4.867.23 kg/m | +79% | -31% |
| NPS 2 | 2.37560.32 mm | 0.1543.91 mm | 0.3448.74 mm | 2.06752.50 mm | 1.68742.85 mm | 3.655.44 kg/m | 7.4611.10 kg/m | +104% | -33% |
| NPS 2 1/2 | 2.87573.02 mm | 0.2035.16 mm | 0.3759.52 mm | 2.46962.71 mm | 2.12553.97 mm | 5.798.62 kg/m | 10.0114.90 kg/m | +73% | -26% |
| NPS 3 | 3.50088.90 mm | 0.2165.49 mm | 0.43811.13 mm | 3.06877.93 mm | 2.62466.65 mm | 7.5811.27 kg/m | 14.3221.32 kg/m | +89% | -27% |
| NPS 4 | 4.500114.30 mm | 0.2376.02 mm | 0.53113.49 mm | 4.026102.26 mm | 3.43887.33 mm | 10.7916.06 kg/m | 22.5133.50 kg/m | +109% | -27% |
| NPS 5 | 5.563141.30 mm | 0.2586.55 mm | 0.62515.88 mm | 5.047128.19 mm | 4.313109.55 mm | 14.6221.75 kg/m | 32.9649.05 kg/m | +125% | -27% |
| NPS 6 | 6.625168.27 mm | 0.2807.11 mm | 0.71918.26 mm | 6.065154.05 mm | 5.187131.75 mm | 18.9728.24 kg/m | 45.3567.49 kg/m | +139% | -27% |
| NPS 8 | 8.625219.07 mm | 0.3228.18 mm | 0.90623.01 mm | 7.981202.72 mm | 6.813173.05 mm | 28.5542.49 kg/m | 74.69111.15 kg/m | +162% | -27% |
| NPS 10 | 10.750273.05 mm | 0.3659.27 mm | 1.12528.57 mm | 10.020254.51 mm | 8.500215.90 mm | 40.4860.25 kg/m | 115.65172.10 kg/m | +186% | -28% |
| NPS 12 | 12.750323.85 mm | 0.40610.31 mm | 1.31233.32 mm | 11.938303.23 mm | 10.126257.20 mm | 53.5379.65 kg/m | 160.27238.51 kg/m | +199% | -28% |
| NPS 14 | 14.000355.60 mm | 0.43811.13 mm | 1.40635.71 mm | 13.124333.35 mm | 11.188284.18 mm | 63.4494.41 kg/m | 189.12281.43 kg/m | +198% | -27% |
| NPS 16 | 16.000406.40 mm | 0.50012.70 mm | 1.59440.49 mm | 15.000381.00 mm | 12.812325.42 mm | 82.77123.18 kg/m | 245.25364.97 kg/m | +196% | -27% |
| NPS 18 | 18.000457.20 mm | 0.56214.27 mm | 1.78145.24 mm | 16.876428.65 mm | 14.438366.73 mm | 104.67155.76 kg/m | 308.51459.11 kg/m | +195% | -27% |
| NPS 20 | 20.000508.00 mm | 0.59415.09 mm | 1.96950.01 mm | 18.812477.82 mm | 16.062407.97 mm | 123.11183.21 kg/m | 379.18564.28 kg/m | +208% | -27% |
| NPS 24 | 24.000609.60 mm | 0.68817.48 mm | 2.34459.54 mm | 22.624574.65 mm | 19.312490.52 mm | 171.30254.92 kg/m | 542.14806.80 kg/m | +216% | -27% |
Bore, weight and flow area are derived from the published outside diameter and wall thickness. Weight is bare steel pipe: w = 10.6802 × t × (OD − t).
Where Schedule 160 actually appears
Small-bore high-pressure process lines, boiler feedwater and blowdown, steam drum connections, hydraulic and lube-oil piping, and vent and drain nipples off high-pressure headers — where the pipe is short, the pressure is high, and the wall is bought for mechanical robustness as much as for hoop stress. Above NPS 12, Schedule 160 is rare in new work: at those diameters the required wall is usually specified directly rather than by schedule.
Full tables: Schedule 40 · Schedule 160 · XS vs XXS · wall thickness from pressure.
Common questions
How much stronger is Schedule 160 than Schedule 40?
Roughly in proportion to wall thickness — commonly 1.8 to 2.3 times in small bore. Pressure capacity is close to linear in wall thickness for thin-walled pipe, so a wall that is twice as thick carries close to twice the pressure in the same material.
Is Schedule 160 available in every size?
No. B36.10M publishes Schedule 160 from NPS 1/2 upward, and it is not listed for the smallest three sizes or for several of the largest ones. Check the size before specifying it.
Should I use Schedule 160 or XXS?
They are different walls and neither is uniformly heavier. In some sizes XXS is thicker than Schedule 160, in others the reverse. Compare the actual walls for the size rather than assuming a ranking.
Does Schedule 160 need special fittings?
The buttweld fittings are the same B16.9 dimensions — those depend on NPS only — but they must be ordered in the matching wall, and the end preparation for a heavy wall differs from the standard bevel.