Pipe Schedule Chart

A pipe schedule is a wall thickness series, not a pressure rating: for a given nominal size, a higher schedule number means a thicker wall. This chart lists the wall thickness in millimetres for every schedule in ASME B36.10M, from NPS 1/8 to NPS 24, with the outside diameter each one is measured against.

Download PDF — Pipe Schedule Wall Thickness Chart

Carbon and low-alloy steel pipe — ASME B36.10M

Wall thickness in millimetres. A dash means the schedule is not a standard size for that nominal size in ASME B36.10M.

Stainless steel pipe — ASME B36.19M

Stainless steel pipe keeps the same outside diameters but uses its own thinner series, written with an S: SCH 5S, 10S, 40S and 80S. The outside diameter is unchanged, so a stainless pipe and a carbon steel pipe of the same nominal size fit the same fittings and flanges; only the bore and the weight differ.

Wall thickness in millimetres, ASME B36.19M.

How the schedule system works

The schedule number was originally derived from the ratio of internal pressure to allowable stress, which is why an old rule of thumb says that a higher schedule number carries a higher pressure. That relationship stopped holding across the whole size range decades ago, and today the schedule number is simply a label for a wall thickness in a table. It tells you how thick the wall is; it does not by itself tell you what pressure the pipe will take.

STD, XS and XXS

Three names in the chart are not numbers. STD, standard wall, equals SCH 40 up to NPS 10 and becomes a fixed 9.53 mm from NPS 12 upward. XS, extra strong, equals SCH 80 up to NPS 8 and becomes a fixed 12.70 mm from NPS 10 upward. XXS, double extra strong, is thicker than SCH 160 in the small sizes and thinner than it in the large sizes. Because the equivalence changes with size, STD and SCH 40 should never be treated as the same specification without checking the nominal size.

If you need a pressure rating rather than a wall thickness

Pressure capacity depends on wall thickness, outside diameter, the grade’s allowable stress and the design temperature together, so it cannot be read off this chart. For a line that must carry a stated pressure, give us the design pressure, the temperature, the grade and the size, and the wall thickness follows from the calculation. ASME B31.3 and B31.8 are the usual design codes for process and transmission piping respectively.

Turning a schedule into a weight

Once you have the wall thickness, the weight follows from the outside diameter: W = 0.0246615 × t × (D − t) kg/m. The weight chart tabulates the result for the common schedules, and the weight calculator works out any size and wall thickness you enter. For the dimensions themselves, see the steel pipe size chart.

Frequently asked questions

Where to go next

• Line pipe and steel pipe – seamless, ERW, LSAW and SSAW to API 5L, ASTM A106, A53, A333, A335 and A312
• Casing and tubing (OCTG) – API 5CT well casing and tubing, J55 through P110 and Q125
• API 5L X65 pipe – grade page with chemistry, mechanical properties and size range
• ASTM A106 Grade B pipe – the high-temperature seamless grade most often quoted with these charts
• Steel pipe weight calculator – work out the weight of any size and wall thickness
• Pipe schedule chart – wall thickness for every schedule
• Steel pipe size chart – outside diameter, wall thickness and inside diameter
• Steel pipe weight chart – nominal weight per metre and per foot
• Product line card – the five product lines and the standards behind each, as a one-page PDF
• All resources and tools – the calculator, the charts and the downloadable PDFs in one place