Pipe Schedule Chart — Wall Thickness, OD & Weight per ASME B36.10M

By Ayush Jaiswal · Precision · 12 yrs

A pipe schedule is a dimensionless number defined by ASME B36.10M that designates the standard wall thickness of a steel pipe at a given nominal pipe size (NPS). Higher schedule numbers mean thicker walls, greater pressure capacity, and heavier weight per metre. This reference chart covers the most commonly procured schedules in India — from thin-wall Schedule 10 through the heavy-duty XXS (Double Extra Strong).

NPS vs Actual OD: For sizes NPS 1/8″ through 12″, the nominal size does not equal the outside diameter. A “2-inch pipe” actually has an OD of 60.3 mm. From NPS 14″ upward the NPS equals the OD in inches. The metric equivalent is DN (Diamètre Nominal) — for example, NPS 2″ = DN 50.

Why schedules matter for procurement: When you order pipe by schedule, you are specifying a precise wall thickness (and therefore a known weight per metre and pressure rating). Misquoting schedule numbers — e.g. ordering Schedule 40 when the design calls for Schedule 80 — can result in under-specced piping that fails hydro test or, conversely, over-spending on unnecessarily thick pipe.

Note: For NPS ≤ 10″, Schedule 40 = STD (Standard wall). For NPS ≤ 8″, Schedule 80 = XS (Extra Strong). Above these sizes, STD and XS have fixed wall thicknesses that differ from Schedule 40/80. XXS (Double Extra Strong) is a separate designation and is not equal to any numbered schedule.

Pipe Schedule Wall Thickness & Weight Chart

Each cell shows Wall Thickness (mm) / Weight (kg/m). A dash (—) indicates the schedule is not defined for that NPS. Weight is calculated using the formula: W = (OD − WT) × WT × 0.02466.

NPS	DN (mm)	OD (mm)	Sch 10 WT / kg/m	Sch 20 WT / kg/m	Sch 40 (STD) WT / kg/m	Sch 80 (XS) WT / kg/m	Sch 160 WT / kg/m	XXS WT / kg/m
1/8"	6	10.3	—	—	1.73 / 0.37	2.41 / 0.47	—	—
1/4"	8	13.7	—	—	2.24 / 0.63	3.02 / 0.80	—	—
3/8"	10	17.1	—	—	2.31 / 0.84	3.2 / 1.10	—	—
1/2"	15	21.3	1.65 / 0.80	—	2.77 / 1.27	3.73 / 1.62	4.78 / 1.95	7.47 / 2.55
3/4"	20	26.7	1.65 / 1.02	—	2.87 / 1.69	3.91 / 2.20	5.56 / 2.90	7.82 / 3.64
1"	25	33.4	1.65 / 1.29	—	3.38 / 2.50	4.55 / 3.24	6.35 / 4.24	9.09 / 5.45
1-1/4"	32	42.2	1.65 / 1.65	—	3.56 / 3.39	4.85 / 4.47	6.35 / 5.61	9.7 / 7.77
1-1/2"	40	48.3	1.65 / 1.90	—	3.68 / 4.05	5.08 / 5.41	7.14 / 7.25	10.15 / 9.55
2"	50	60.3	1.65 / 2.39	—	3.91 / 5.44	5.54 / 7.48	8.74 / 11.11	11.07 / 13.44
2-1/2"	65	73	2.11 / 3.69	—	5.16 / 8.63	7.01 / 11.41	9.53 / 14.92	14.02 / 20.39
3"	80	88.9	2.11 / 4.52	—	5.49 / 11.29	7.62 / 15.27	11.13 / 21.35	15.24 / 27.68
3-1/2"	90	101.6	2.11 / 5.18	—	5.74 / 13.57	8.08 / 18.63	—	—
4"	100	114.3	2.11 / 5.84	—	6.02 / 16.07	8.56 / 22.32	13.49 / 33.54	17.12 / 41.03
5"	125	141.3	2.77 / 9.46	—	6.55 / 21.77	9.53 / 30.97	15.88 / 49.11	19.05 / 57.43
6"	150	168.3	2.77 / 11.31	—	7.11 / 28.26	10.97 / 42.56	18.26 / 67.56	21.95 / 79.22
8"	200	219.1	2.77 / 14.78	6.35 / 33.31	8.18 / 42.55	12.7 / 64.64	23.01 / 111.27	22.23 / 107.92
10"	250	273.1	3.4 / 22.61	6.35 / 41.77	9.27 / 60.31	12.7 / 81.55	28.58 / 172.33	25.4 / 155.15
12"	300	323.8	3.96 / 31.23	6.35 / 49.71	10.31 / 79.70	12.7 / 97.43	33.32 / 238.68	25.4 / 186.91
14"	350	355.6	3.96 / 34.34	7.92 / 67.90	11.13 / 94.55	12.7 / 107.39	35.71 / 281.70	—
16"	400	406.4	4.19 / 41.56	7.92 / 77.83	12.7 / 123.30	14.27 / 137.99	40.49 / 365.36	—
18"	450	457.2	4.19 / 46.81	7.92 / 87.75	14.27 / 155.87	15.88 / 172.82	45.24 / 459.59	—
20"	500	508	4.78 / 59.32	9.53 / 117.15	15.09 / 183.42	20.62 / 247.83	44.45 / 508.11	—
24"	600	609.6	5.54 / 82.52	9.53 / 141.02	17.48 / 255.24	24.61 / 355.02	52.37 / 719.63	—

Weight Calculation Formula

Weight (kg/m) = (OD − WT) × WT × 0.02466

OD = Outer Diameter in millimeters (mm)
WT = Wall Thickness in millimeters (mm)
0.02466 = constant derived from π × ρ / 1,000,000 where ρ = 7850 kg/m³ (carbon steel density)

Frequently Asked Questions

Q.What is pipe schedule?

Pipe schedule is a dimensionless number defined by ASME B36.10M that designates the wall thickness of a pipe for a given NPS (Nominal Pipe Size). A higher schedule number means a thicker wall and higher pressure rating. Common schedules are 10, 20, 30, 40, 60, 80, 100, 120, 140, and 160, plus the legacy designations STD (Standard), XS (Extra Strong), and XXS (Double Extra Strong).

Q.What is the difference between Schedule 40 and Schedule 80?

Schedule 80 pipes have a thicker wall than Schedule 40 for the same NPS. For example, a 2" NPS pipe has a wall thickness of 3.91 mm in Schedule 40 versus 5.54 mm in Schedule 80. This makes Schedule 80 pipes heavier per metre, able to withstand higher internal pressures, and more expensive. Schedule 40 is used for general-purpose water, gas, and structural service, while Schedule 80 is specified for high-pressure steam, chemical, and industrial process lines.

Q.What does NPS mean?

NPS stands for Nominal Pipe Size. It is a North American designation system for pipe dimensions that does not directly correspond to any physical measurement of the pipe. For NPS 1/8" through 12", the actual outside diameter (OD) is larger than the nominal size. From NPS 14" upwards, the NPS equals the OD in inches. NPS is used alongside the metric DN (Diamètre Nominal) system — for example, NPS 2" = DN 50.

Q.How is pipe wall thickness related to schedule number?

The original schedule formula is: Schedule Number = 1000 × (P / S), where P is the internal working pressure (psi) and S is the allowable stress (psi) of the pipe material. In practice, ASME B36.10M standardised specific wall thicknesses for each NPS/schedule combination. Two pipes of the same schedule but different NPS will have different wall thicknesses. For procurement, always specify both NPS and schedule (or the exact wall thickness) to avoid ambiguity.

Q.What is the standard pipe schedule for water supply?

Schedule 40 (also designated STD for sizes up to NPS 10") is the most commonly used schedule for potable water supply, fire protection, and plumbing in India. For municipal water mains and higher-pressure applications, Schedule 80 may be specified. In residential and low-rise construction using IS 1239 ERW pipes, Medium (Class B) grade closely matches Schedule 40 wall thickness for common NPS sizes.

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Pipe Schedule Dimensions Chart

Pipe Schedule Wall Thickness & Weight Chart

Weight Calculation Formula

Frequently Asked Questions

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