Pipe schedule chart: Sch 40, 80, 160 in mm and kg/m

A 2-inch Schedule 40 pipe has an outside diameter of 60.3 mm and a 3.91 mm wall and weighs 5.44 kg/m; Schedule 80 of the same size has a 5.54 mm wall and weighs 7.48 kg/m. The size (NPS) fixes the outside diameter, the schedule only sets the wall. Below: NPS 1/8 to 24 (DN 6–600) in millimetres for Sch 10, 40, 80, 160 and XXS to ASME B36.10M, the STD and XS classes, stainless 5S–80S to ASME B36.19M, and how the American series differs from EN 10220.

Short answer

Sch 40 = STD up to NPS 10, Sch 80 = XS up to NPS 8. Common sizes in Sch 40: 1/2″ — 21.3 × 2.77 mm (1.27 kg/m), 1″ — 33.4 × 3.38 mm (2.50 kg/m), 2″ — 60.3 × 3.91 mm (5.44 kg/m), 4″ — 114.3 × 6.02 mm (16.08 kg/m), 6″ — 168.3 × 7.11 mm (28.26 kg/m). The outside diameter of a size never changes; a heavier schedule eats into the bore. Every row of the main table has its own anchor: NPS 2, DN 100.

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What Schedule and NPS mean

NPS (Nominal Pipe Size) is a size label, not a measurement. Up to NPS 12 the real outside diameter is larger than the number of inches: a 2″ pipe is 60.3 mm (2.375 in) across, a 1/2″ pipe 21.3 mm. From NPS 14 the outside diameter equals the size: NPS 14 is 355.6 mm (14.000 in). DN is the metric label of the same pipe (NPS 2 = DN 50, NPS 4 = DN 100), so DN does not give the diameter either.

Schedule (Sch) is the wall-thickness series. Within one size the outside diameter stays put and the wall grows from Sch 10 through 40 and 80 to 160, so the bore shrinks. The same schedule means a different wall on different sizes: Sch 40 is 2.77 mm on NPS 1/2 and 9.27 mm on NPS 10. Besides the numbered schedules, ASME B36.10M keeps the older weight classes STD (standard), XS (extra strong) and XXS (double extra strong); for stainless steel ASME B36.19M adds the S series — 5S, 10S, 40S, 80S.

Wall thickness by schedule, mm (ASME B36.10M)

Carbon and alloy steel pipe, welded and seamless. Outside diameter in mm and inches, wall in mm; a dash means the size has no such wall in the standard or two of our sources do not confirm it. Each row has an anchor — #nps-2, #dn-50 and so on.

Jump to size: 1/8″ · 1/4″ · 3/8″ · 1/2″ · 3/4″ · 1″ · 1 1/4″ · 1 1/2″ · 2″ · 2 1/2″ · 3″ · 3 1/2″ · 4″ · 5″ · 6″ · 8″ · 10″ · 12″ · 14″ · 16″ · 18″ · 20″ · 22″ · 24″

For NPS 1/8, 1/4 and 3/8 we give no Sch 160 or XXS: only one of our sources lists them. NPS 3 1/2 has no Sch 160 here, and NPS 14 and up no XXS. Note NPS 8: XXS (22.23 mm) is thinner than Sch 160 (23.01 mm) — the weight classes and the schedules are two separate series.

Weight of schedule pipe, kg/m

Plain-end mass of carbon steel pipe (7.85 g/cm³) from the formula m = 0.0246615 · s · (D − s), where D is the outside diameter and s the wall, both in mm; 0.0246615 is π · 7.85 / 1000. Every value has been checked against the mass in a source table.

Example: 4″ Sch 40 — 0.0246615 · 6.02 · (114.3 − 6.02) = 16.08 kg/m, so a 6 m length weighs 96.5 kg; the same length in Sch 80 weighs 133.9 kg. For other sizes and for EN tube use the pipe weight calculator.

STD and XS: where they part from Sch 40 and Sch 80

STD equals Sch 40 up to NPS 10 and XS equals Sch 80 up to NPS 8. Above that STD stays at 9.53 mm (0.375 in) and XS at 12.70 mm (0.500 in), while the schedules keep growing: on NPS 12 Sch 40 is 10.31 mm against 9.53 for STD, and Sch 80 is 17.48 mm against 12.70 for XS. ASTM A53 pipe tables list both the class and the schedule:

If a drawing says “NPS 12 Sch 40”, STD pipe will not do: it is 0.78 mm thinner and 5.85 kg/m lighter. Check which of the two the specification asks for.

Stainless steel pipe: 5S, 10S, 40S, 80S (ASME B36.19M)

Stainless pipe (ASTM A312 and similar) has the same outside diameters as B36.10M and its own S series. 40S and 80S match Sch 40 and Sch 80 up to NPS 10; on NPS 12 40S is 9.53 mm (Sch 40 — 10.31) and 80S 12.70 mm (Sch 80 — 17.48). 5S and 10S are thin walls for low-pressure lines. Wall, mm:

For NPS 14–24 we give only 5S and 10S: 40S and 80S for these sizes appear in one of our sources and are missing from the other two, so take the wall from the order and the mill certificate. NPS 22 is left out for the same reason.

Stainless pipe weight, kg/m

Mass of 1.4301 (304) pipe at a density of 7.90 g/cm³; 1.4404 (316L), 8.00 g/cm³, is 1.3 % heavier. 2″ 10S weighs 3.96 kg/m in 304 and 4.01 kg/m in 316L. Stainless tube in EN and DIN sizes is in the stainless tube weight calculator.

NPS, DN and outside diameter against EN 10220

Both systems use DN, but not the same outside diameter. European pipe to EN 10220 (seamless EN 10216 and welded EN 10217 tube are made in that series) matches ASME at DN 15, 40, 50, 80, 100, 150 and 200; at DN 20, 25 and 32 it is 0.2–0.3 mm larger, and at DN 65 and DN 125 the two are different pipes altogether:

In practice: a fitting or flange ordered by NPS (ASME B16.9, B16.5) is made for the ASME diameter. At DN 65 (73.0 against 76.1 mm) and DN 125 (141.3 against 139.7 mm) EN pipe will not fit an ASME fitting at all; at DN 20–32 the 0.2–0.3 mm leaves a small step at the root of a butt weld. The walls are specified differently too: “DN 50 Sch 40” names an ASME wall (3.91 mm), while an EN order gives D × T in millimetres from the EN series. The European series with masses is in the DN and inch table of the pipe weight calculator.

Example: choosing pipe by schedule

A compressed-air line in NPS 2, carbon steel, Sch 40 on the drawing: order 60.3 × 3.91 mm pipe, 5.44 kg/m, bore 52.5 mm. Ten 6 m lengths weigh 326 kg. If Sch 80 (5.54 mm) is what the stores have, the outside diameter, fittings and flanges stay the same, the bore drops to 49.2 mm and the weight rises to 449 kg — and every butt joint has more metal to fill. Going the other way, Sch 10 (2.77 mm, 3.93 kg/m) is lighter, but whether it holds the pressure is decided by the design calculation, not by this table. Bevel to the wall you actually have — see joint preparation — and mark out branches with the pipe cutting template.

Where next

Weight of any tube or hollow section — pipe weight calculator; stainless tube to EN and DIN — stainless tube calculator; STD, XS and round HSS in lb/ft — steel pipe weight chart; positions and technique for pipe joints — pipe welding positions.

Author: Dmitry Frolov, welder and metal fabricator Updated: 24 October 2026