Nps Pipe Chart

Nominal Pipe Size (NPS) is the North American system for steel pipe sizes, and the nominal number rarely equals any actual dimension. This chart lists the outside diameter, Schedule 40 and Schedule 80 wall thickness, inside diameter, approximate weight per foot for carbon steel and the metric DN equivalent for each size from 1/8 inch to 24 inch.

NPS pipe chart: Schedule 40 and 80

Dimensions follow ASME B36.10M for welded and seamless wrought steel pipe. Stainless steel pipe to ASME B36.19M uses the same outside diameters, but its “S” schedules (such as 10S, 40S and 80S) can differ from carbon steel schedules at larger sizes.

How NPS works

For NPS 1/8 through 12, the nominal size is a historical approximation of the inside diameter of the original standard-weight pipe, which is why a 2-inch pipe has an outside diameter of 2.375 inches. For NPS 14 and above, the nominal size equals the outside diameter. Within a size, the outside diameter stays the same for every schedule, so fittings fit; heavier schedules gain wall thickness on the inside, reducing the bore.

What schedule means

The schedule number describes wall thickness. Schedule 40 is the most common for general piping; Schedule 80 is thicker for higher pressures and more corrosion or thread allowance. Other schedules include 5, 10, 20, 30, 60, 100, 120, 140 and 160, as well as weight classes STD (standard), XS (extra strong) and XXS (double extra strong). For NPS 10 and smaller, STD matches Schedule 40 and XS matches Schedule 80; at larger sizes they diverge.

Weight per foot

Plain-end carbon steel weight is approximately 10.69 × (OD − t) × t pounds per foot, with OD and wall thickness t in inches. Published tables may differ slightly because of rounding and the density used.

NPS and DN

DN (diamètre nominal) is the metric designation used in ISO and European standards; like NPS, it is a nominal size rather than an exact dimension. Common pairs are NPS 1/2 = DN 15, NPS 1 = DN 25, NPS 2 = DN 50, NPS 4 = DN 100 and NPS 6 = DN 150. The outside diameters of NPS pipe and some metric pipe standards differ, so check compatibility before mixing systems.

Worked example

An engineer needs the inside diameter of 3-inch Schedule 80 pipe to size a flow calculation. The chart gives an OD of 3.500 in and a wall of 0.300 in, so the ID is 3.500 − 2 × 0.300 = 2.900 in. The weight is about 10.69 × (3.5 − 0.3) × 0.3 = 10.26 lb/ft, so a 21-foot random length weighs about 215 lb before fittings.

Pipe vs tube

Pipe is specified by nominal size and schedule, and its OD is fixed for each size; tube (such as copper tube or hydraulic tube) is usually specified by actual outside diameter and wall thickness. Copper water tube in North America has its own nominal sizes (types K, L and M) that do not match steel NPS dimensions. Always check which system a drawing or fitting uses.

What is in the template pack

• Printable NPS chart — sizes 1/8 to 24 inch with OD, Sch 40 and Sch 80 wall and ID, and DN.
• Excel pipe chart — the same data with weight per foot, flow area and volume per foot calculated.
• Pipe schedule quick reference — what the schedules and weight classes mean.
• Take-off sheet — list pipe runs, sizes, lengths and fittings for estimating.

Formats

PDF charts (US Letter) and Excel workbooks with formulas. Always confirm critical dimensions against the current standard or the manufacturer’s data for your application.