Schedule 10 vs Schedule 40 Pipe
Thin wall against the default wall: what Schedule 10 saves in weight, what it gains in bore, and the corrosion allowance and threading it gives up.
- Sizes with both
- 26
- Weight saved by Sch 10
- 43% on average
- Flow area gained
- +12% on average
- Common use
- Sch 10 — low-pressure and stainless
Short answer. Schedule 10 is a thin-wall pipe: same outside diameter as Schedule 40, about 43% lighter, and a larger bore. It is the standard choice for low-pressure stainless process lines and for large-diameter water service where Schedule 40 is far heavier than the pressure requires. Schedule 40 remains the default for carbon steel utility piping and anything threaded.
Thin wall, same envelope
At NPS 6 the wall drops from 0.280 in (7.1 mm) in Schedule 40 to 0.134 in (3.4 mm) in Schedule 10 — 52% less metal. Weight falls from 18.97 lb/ft to 9.29 lb/ft, which changes what the pipe can be hung from and how many people it takes to place a spool.
The gain is not only weight. The bore grows from 6.065 in (154.1 mm) to 6.357 in (161.5 mm), so flow area rises 10% and the same duty runs at lower velocity and lower pressure drop.
Dimensions are given in inches, with the millimetre equivalent beneath in grey.
| NPS | OD | Sch 10 wall | Sch 40 wall | Sch 10 bore | Sch 40 bore | Sch 10 weight | Sch 40 weight | Weight change | Flow area change |
|---|---|---|---|---|---|---|---|---|---|
| NPS 1/8 | 0.40510.29 mm | 0.0491.24 mm | 0.0681.73 mm | 0.3077.80 mm | 0.2696.83 mm | 0.190.28 kg/m | 0.240.36 kg/m | +31% | -23% |
| NPS 1/4 | 0.54013.72 mm | 0.0651.65 mm | 0.0882.24 mm | 0.41010.41 mm | 0.3649.25 mm | 0.330.49 kg/m | 0.420.63 kg/m | +29% | -21% |
| NPS 3/8 | 0.67517.14 mm | 0.0651.65 mm | 0.0912.31 mm | 0.54513.84 mm | 0.49312.52 mm | 0.420.63 kg/m | 0.570.84 kg/m | +34% | -18% |
| NPS 1/2 | 0.84021.34 mm | 0.0832.11 mm | 0.1092.77 mm | 0.67417.12 mm | 0.62215.80 mm | 0.671.00 kg/m | 0.851.27 kg/m | +27% | -15% |
| NPS 3/4 | 1.05026.67 mm | 0.0832.11 mm | 0.1132.87 mm | 0.88422.45 mm | 0.82420.93 mm | 0.861.28 kg/m | 1.131.68 kg/m | +32% | -13% |
| NPS 1 | 1.31533.40 mm | 0.1092.77 mm | 0.1333.38 mm | 1.09727.86 mm | 1.04926.64 mm | 1.402.09 kg/m | 1.682.50 kg/m | +20% | -9% |
| NPS 1 1/4 | 1.66042.16 mm | 0.1092.77 mm | 0.1403.56 mm | 1.44236.63 mm | 1.38035.05 mm | 1.812.69 kg/m | 2.273.38 kg/m | +26% | -8% |
| NPS 1 1/2 | 1.90048.26 mm | 0.1092.77 mm | 0.1453.68 mm | 1.68242.72 mm | 1.61040.89 mm | 2.083.10 kg/m | 2.724.04 kg/m | +30% | -8% |
| NPS 2 | 2.37560.32 mm | 0.1092.77 mm | 0.1543.91 mm | 2.15754.79 mm | 2.06752.50 mm | 2.643.93 kg/m | 3.655.44 kg/m | +38% | -8% |
| NPS 2 1/2 | 2.87573.02 mm | 0.1203.05 mm | 0.2035.16 mm | 2.63566.93 mm | 2.46962.71 mm | 3.535.25 kg/m | 5.798.62 kg/m | +64% | -12% |
| NPS 3 | 3.50088.90 mm | 0.1203.05 mm | 0.2165.49 mm | 3.26082.80 mm | 3.06877.93 mm | 4.336.45 kg/m | 7.5811.27 kg/m | +75% | -11% |
| NPS 3 1/2 | 4.000101.60 mm | 0.1203.05 mm | 0.2265.74 mm | 3.76095.50 mm | 3.54890.12 mm | 4.977.40 kg/m | 9.1113.56 kg/m | +83% | -11% |
| NPS 4 | 4.500114.30 mm | 0.1203.05 mm | 0.2376.02 mm | 4.260108.20 mm | 4.026102.26 mm | 5.618.35 kg/m | 10.7916.06 kg/m | +92% | -11% |
| NPS 5 | 5.563141.30 mm | 0.1343.40 mm | 0.2586.55 mm | 5.295134.49 mm | 5.047128.19 mm | 7.7711.56 kg/m | 14.6221.75 kg/m | +88% | -9% |
| NPS 6 | 6.625168.27 mm | 0.1343.40 mm | 0.2807.11 mm | 6.357161.47 mm | 6.065154.05 mm | 9.2913.82 kg/m | 18.9728.24 kg/m | +104% | -9% |
| NPS 8 | 8.625219.07 mm | 0.1483.76 mm | 0.3228.18 mm | 8.329211.56 mm | 7.981202.72 mm | 13.4019.94 kg/m | 28.5542.49 kg/m | +113% | -8% |
| NPS 10 | 10.750273.05 mm | 0.1654.19 mm | 0.3659.27 mm | 10.420264.67 mm | 10.020254.51 mm | 18.6527.76 kg/m | 40.4860.25 kg/m | +117% | -8% |
| NPS 12 | 12.750323.85 mm | 0.1804.57 mm | 0.40610.31 mm | 12.390314.71 mm | 11.938303.23 mm | 24.1735.96 kg/m | 53.5379.65 kg/m | +122% | -7% |
| NPS 14 | 14.000355.60 mm | 0.1884.78 mm | 0.43811.13 mm | 13.624346.05 mm | 13.124333.35 mm | 27.7341.27 kg/m | 63.4494.41 kg/m | +129% | -7% |
| NPS 16 | 16.000406.40 mm | 0.1884.78 mm | 0.50012.70 mm | 15.624396.85 mm | 15.000381.00 mm | 31.7547.25 kg/m | 82.77123.18 kg/m | +161% | -8% |
| NPS 18 | 18.000457.20 mm | 0.1884.78 mm | 0.56214.27 mm | 17.624447.65 mm | 16.876428.65 mm | 35.7653.22 kg/m | 104.67155.76 kg/m | +193% | -8% |
| NPS 20 | 20.000508.00 mm | 0.2185.54 mm | 0.59415.09 mm | 19.564496.93 mm | 18.812477.82 mm | 46.0668.54 kg/m | 123.11183.21 kg/m | +167% | -8% |
| NPS 24 | 24.000609.60 mm | 0.2506.35 mm | 0.68817.48 mm | 23.500596.90 mm | 22.624574.65 mm | 63.4194.37 kg/m | 171.30254.92 kg/m | +170% | -7% |
| NPS 32 | 32.000812.80 mm | 0.3127.92 mm | 0.68817.48 mm | 31.376796.95 mm | 30.624777.85 mm | 105.59157.14 kg/m | 230.08342.40 kg/m | +118% | -5% |
| NPS 34 | 34.000863.60 mm | 0.3127.92 mm | 0.68817.48 mm | 33.376847.75 mm | 32.624828.65 mm | 112.26167.05 kg/m | 244.78364.27 kg/m | +118% | -4% |
| NPS 36 | 36.000914.40 mm | 0.3127.92 mm | 0.75019.05 mm | 35.376898.55 mm | 34.500876.30 mm | 118.92176.97 kg/m | 282.36420.19 kg/m | +137% | -5% |
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).
What thin wall costs you
Schedule 10 cannot be threaded — there is not enough wall to cut a thread into and keep a pressure boundary. It has effectively no corrosion allowance, which is why it is specified in stainless and rarely in bare carbon steel. It dents and buckles under support point loads that Schedule 40 shrugs off, so support spacing and shoe design have to be checked rather than taken from a standard table.
Schedule 10 suits
- Stainless process lines where the material, not the wall, provides the corrosion resistance
- Large-diameter low-pressure water, air and vent service
- Roll-grooved and clamp-coupled systems
- Weight-critical work: modules, racks, offshore
- Service where cost of alloy is dominated by wall thickness
Schedule 40 suits
- Carbon steel utility service needing a corrosion allowance
- Anything threaded
- Ordinary process pressures in NPS 2 and below
- Buried, impacted or vibrating lines
- Work where the stocked, standard item beats the optimal one
Full tables: Schedule 10 dimensions · Schedule 40 dimensions · the stainless S-schedules · B36.19M stainless.
Common questions
Is Schedule 10 strong enough for compressed air?
Often yes at shop pressures, but it must be calculated rather than assumed. Compressed gas stores energy, so a thin-wall failure is energetic — many owners specify Schedule 40 minimum for air regardless of the calculation.
Can Schedule 10 pipe be threaded?
No. The wall is too thin to carry a thread and still hold pressure. Schedule 10 is joined by welding, roll-grooved couplings or flanges.
Why is Schedule 10 so common in stainless?
Because stainless does not need a corrosion allowance in most services, and stainless is expensive by weight. Removing wall that exists only for corrosion removes cost. B36.19M formalises this with the 10S schedule.
Is Schedule 10 the same as 10S?
In every size where B36.19M publishes 10S, the wall matches Schedule 10 — but B36.19M stops at NPS 30, and 10S carries the stainless material and tolerance requirements that Schedule 10 alone does not.