Workshop reference

Pipe Schedule Chart and Pipe Size Chart

Steel pipe sizes from NPS 1/8 to 24: DN, outside diameter and wall thickness for Schedule 10, 40, STD, 80, XS, 160 and XXS, in inches and millimeters. Schedule 40 and 80 also get inside diameter and weight. Every figure follows ASME B36.10M and appears in at least two published tables, and the cells where the tables disagree are listed at the bottom.

The short answer

NPS is a name, not a measurement. Up to NPS 12 the outside diameter is bigger than the number: 2 inch pipe measures 2.375 in (60.3 mm) across. From NPS 14 up the two match. The schedule only changes the wall: the outside diameter of an NPS never moves, so a higher schedule means a thicker wall and a smaller bore.

Jump to the chart Schedule 40 dimensions

Quick answers

The pipe size questions that come up most, answered from the tables below.

Quick answers on pipe sizes and schedules
Question	Answer
Outside diameter of 2 inch pipe	2.375 in (60.3 mm), whatever the schedule.
Wall of 2 inch Schedule 40	0.154 in (3.91 mm), which leaves a bore of 2.067 in (52.5 mm).
Wall of 2 inch Schedule 80	0.218 in (5.54 mm), which leaves a bore of 1.939 in (49.3 mm).
NPS 1 1/2 in DN	DN 40, with an outside diameter of 1.900 in (48.3 mm).
Outside diameter of 4 inch pipe	4.500 in (114.3 mm). The Schedule 40 wall is 0.237 in (6.02 mm).
Outside diameter of 1/2 inch pipe	0.840 in (21.3 mm), not half an inch. It is DN 15, and the Schedule 40 bore is 0.622 in.
Is Schedule 40 the same as STD?	Yes up to NPS 10. From NPS 12 they differ: STD is 0.375 in and Schedule 40 is 0.406 in.
Is Schedule 80 the same as XS?	Yes up to NPS 8. From NPS 10 they differ: XS is 0.500 in and Schedule 80 is 0.594 in.
Weight of 2 inch Schedule 40	3.66 lb/ft (5.44 kg/m), plain end.

Pipe size chart: NPS, DN and outside diameter

NPS stands for nominal pipe size and DN for diameter nominal, the metric version. To go from NPS to DN, read across the row: NPS 1 1/2 is DN 40 and NPS 4 is DN 100. Each size has one outside diameter, and it does not change with schedule. All 24 sizes from NPS 1/8 to 24 are below.

Pipe sizes: NPS, DN and outside diameter in inches and millimeters
NPS	DN	OD (in)	OD (mm)
1/8	6	0.405	10.3
1/4	8	0.540	13.7
3/8	10	0.675	17.1
1/2	15	0.840	21.3
3/4	20	1.050	26.7
1	25	1.315	33.4
1 1/4	32	1.660	42.2
1 1/2	40	1.900	48.3
2	50	2.375	60.3
2 1/2	65	2.875	73.0
3	80	3.500	88.9
3 1/2	90	4.000	101.6
4	100	4.500	114.3
5	125	5.563	141.3
6	150	6.625	168.3
8	200	8.625	219.1
10	250	10.750	273.0
12	300	12.750	323.8
14	350	14.000	355.6
16	400	16.000	406.4
18	450	18.000	457
20	500	20.000	508
22	550	22.000	559
24	600	24.000	610

NPS 12 is the last size whose outside diameter (12.750 in) is larger than its name. From NPS 14 the outside diameter equals the NPS. Millimeter sizes are the ones B36.10M prints: rounded to 0.1 mm, and to the whole millimeter from NPS 18 up. The inch size is the defining figure.

Pipe schedule chart: wall thickness by schedule

Find your NPS down the left and your schedule across the top. The first table is in inches and the second in millimeters. Where B36.10M gives no wall for a size and schedule, the cell says not listed.

Wall thickness in inches

Pipe wall thickness by schedule in inches, NPS 1/8 to 24
NPS	DN	OD (in)	Sch 10	Sch 40	STD	Sch 80	XS	Sch 160	XXS
1/8	6	0.405	0.049	0.068	0.068	0.095	0.095	not listed	not listed
1/4	8	0.540	0.065	0.088	0.088	0.119	0.119	not listed	not listed
3/8	10	0.675	0.065	0.091	0.091	0.126	0.126	not listed	not listed
1/2	15	0.840	0.083	0.109	0.109	0.147	0.147	0.188	0.294
3/4	20	1.050	0.083	0.113	0.113	0.154	0.154	0.219	0.308
1	25	1.315	0.109	0.133	0.133	0.179	0.179	0.250	0.358
1 1/4	32	1.660	0.109	0.140	0.140	0.191	0.191	0.250	0.382
1 1/2	40	1.900	0.109	0.145	0.145	0.200	0.200	0.281	0.400
2	50	2.375	0.109	0.154	0.154	0.218	0.218	0.344	0.436
2 1/2	65	2.875	0.120	0.203	0.203	0.276	0.276	0.375	0.552
3	80	3.500	0.120	0.216	0.216	0.300	0.300	0.438	0.600
3 1/2	90	4.000	0.120	0.226	0.226	0.318	0.318	not listed	not listed
4	100	4.500	0.120	0.237	0.237	0.337	0.337	0.531	0.674
5	125	5.563	0.134	0.258	0.258	0.375	0.375	0.625	0.750
6	150	6.625	0.134	0.280	0.280	0.432	0.432	0.719	0.864
8	200	8.625	0.148	0.322	0.322	0.500	0.500	0.906	0.875
10	250	10.750	0.165	0.365	0.365	0.594	0.500	1.125	1.000
12	300	12.750	0.180	0.406	0.375	0.688	0.500	1.312	1.000
14	350	14.000	0.250	0.438	0.375	0.750	0.500	1.406	not listed
16	400	16.000	0.250	0.500	0.375	0.844	0.500	1.594	not listed
18	450	18.000	0.250	0.562	0.375	0.938	0.500	1.781	not listed
20	500	20.000	0.250	0.594	0.375	1.031	0.500	1.969	not listed
22	550	22.000	0.250	not listed	0.375	1.125	0.500	2.125	not listed
24	600	24.000	0.250	0.688	0.375	1.219	0.500	2.344	not listed

Wall thickness in millimeters

Pipe wall thickness by schedule in millimeters, NPS 1/8 to 24
NPS	DN	OD (mm)	Sch 10	Sch 40	STD	Sch 80	XS	Sch 160	XXS
1/8	6	10.3	1.24	1.73	1.73	2.41	2.41	not listed	not listed
1/4	8	13.7	1.65	2.24	2.24	3.02	3.02	not listed	not listed
3/8	10	17.1	1.65	2.31	2.31	3.20	3.20	not listed	not listed
1/2	15	21.3	2.11	2.77	2.77	3.73	3.73	4.78	7.47
3/4	20	26.7	2.11	2.87	2.87	3.91	3.91	5.56	7.82
1	25	33.4	2.77	3.38	3.38	4.55	4.55	6.35	9.09
1 1/4	32	42.2	2.77	3.56	3.56	4.85	4.85	6.35	9.70
1 1/2	40	48.3	2.77	3.68	3.68	5.08	5.08	7.14	10.15
2	50	60.3	2.77	3.91	3.91	5.54	5.54	8.74	11.07
2 1/2	65	73.0	3.05	5.16	5.16	7.01	7.01	9.53	14.02
3	80	88.9	3.05	5.49	5.49	7.62	7.62	11.13	15.24
3 1/2	90	101.6	3.05	5.74	5.74	8.08	8.08	not listed	not listed
4	100	114.3	3.05	6.02	6.02	8.56	8.56	13.49	17.12
5	125	141.3	3.40	6.55	6.55	9.53	9.53	15.88	19.05
6	150	168.3	3.40	7.11	7.11	10.97	10.97	18.26	21.95
8	200	219.1	3.76	8.18	8.18	12.70	12.70	23.01	22.23
10	250	273.0	4.19	9.27	9.27	15.09	12.70	28.58	25.40
12	300	323.8	4.57	10.31	9.53	17.48	12.70	33.32	25.40
14	350	355.6	6.35	11.13	9.53	19.05	12.70	35.71	not listed
16	400	406.4	6.35	12.70	9.53	21.44	12.70	40.49	not listed
18	450	457	6.35	14.27	9.53	23.83	12.70	45.24	not listed
20	500	508	6.35	15.09	9.53	26.19	12.70	50.01	not listed
22	550	559	6.35	not listed	9.53	28.58	12.70	53.98	not listed
24	600	610	6.35	17.48	9.53	30.96	12.70	59.54	not listed

Sch 10 is the carbon steel schedule from B36.10M. NPS 22 has no Schedule 40, and NPS 3 1/2 has no Schedule 160 and, in the B36.10M tables checked, no XXS (some charts show 0.636 in). At NPS 10 and 12 the XXS wall is 1.000 in, which is also the Schedule 140 wall at NPS 10 and the Schedule 120 wall at NPS 12. Drawings often give a wall as a fraction: STD above NPS 10 is 3/8 in (0.375) and XS is 1/2 in (0.500). The fraction to decimal chart converts the rest.

Schedule 40 pipe dimensions

Schedule 40 wall, inside diameter and plain-end weight for every size that has one. Inside diameter is the outside diameter minus twice the wall. Weight is for plain-end pipe, with no threads or coupling.

Schedule 40 pipe dimensions and plain-end weight, NPS 1/8 to 24
NPS	DN	OD (in)	OD (mm)	Wall (in)	Wall (mm)	ID (in)	ID (mm)	Weight (lb/ft)	Weight (kg/m)
1/8	6	0.405	10.3	0.068	1.73	0.269	6.8	0.24	0.37
1/4	8	0.540	13.7	0.088	2.24	0.364	9.2	0.43	0.63
3/8	10	0.675	17.1	0.091	2.31	0.493	12.5	0.57	0.84
1/2	15	0.840	21.3	0.109	2.77	0.622	15.8	0.85	1.27
3/4	20	1.050	26.7	0.113	2.87	0.824	20.9	1.13	1.69
1	25	1.315	33.4	0.133	3.38	1.049	26.6	1.68	2.50
1 1/4	32	1.660	42.2	0.140	3.56	1.380	35.1	2.27	3.39
1 1/2	40	1.900	48.3	0.145	3.68	1.610	40.9	2.72	4.05
2	50	2.375	60.3	0.154	3.91	2.067	52.5	3.66	5.44
2 1/2	65	2.875	73.0	0.203	5.16	2.469	62.7	5.80	8.63
3	80	3.500	88.9	0.216	5.49	3.068	77.9	7.58	11.29
3 1/2	90	4.000	101.6	0.226	5.74	3.548	90.1	9.12	13.57
4	100	4.500	114.3	0.237	6.02	4.026	102.3	10.80	16.08
5	125	5.563	141.3	0.258	6.55	5.047	128.2	14.63	21.77
6	150	6.625	168.3	0.280	7.11	6.065	154.1	18.99	28.26
8	200	8.625	219.1	0.322	8.18	7.981	202.7	28.58	42.55
10	250	10.750	273.0	0.365	9.27	10.020	254.5	40.52	60.29
12	300	12.750	323.8	0.406	10.31	11.938	303.2	53.57	79.71
14	350	14.000	355.6	0.438	11.13	13.124	333.3	63.50	94.55
16	400	16.000	406.4	0.500	12.70	15.000	381.0	82.85	123.31
18	450	18.000	457	0.562	14.27	16.876	428.7	104.76	155.81
20	500	20.000	508	0.594	15.09	18.812	477.8	123.23	183.43
22	550	22.000	559	not listed
24	600	24.000	610	0.688	17.48	22.624	574.6	171.45	255.43

NPS 22 has no Schedule 40 in the standard. Up to NPS 10 these walls are also the STD walls. From NPS 12 STD stays at 0.375 in, so check which one the drawing means.

Schedule 80 pipe dimensions

Schedule 80 wall, inside diameter and plain-end weight for every size from NPS 1/8 to 24, worked out the same way as the Schedule 40 table.

Schedule 80 pipe dimensions and plain-end weight, NPS 1/8 to 24
NPS	DN	OD (in)	OD (mm)	Wall (in)	Wall (mm)	ID (in)	ID (mm)	Weight (lb/ft)	Weight (kg/m)
1/8	6	0.405	10.3	0.095	2.41	0.215	5.5	0.31	0.47
1/4	8	0.540	13.7	0.119	3.02	0.302	7.7	0.54	0.80
3/8	10	0.675	17.1	0.126	3.20	0.423	10.7	0.74	1.10
1/2	15	0.840	21.3	0.147	3.73	0.546	13.9	1.09	1.62
3/4	20	1.050	26.7	0.154	3.91	0.742	18.8	1.48	2.20
1	25	1.315	33.4	0.179	4.55	0.957	24.3	2.17	3.24
1 1/4	32	1.660	42.2	0.191	4.85	1.278	32.5	3.00	4.47
1 1/2	40	1.900	48.3	0.200	5.08	1.500	38.1	3.63	5.41
2	50	2.375	60.3	0.218	5.54	1.939	49.3	5.03	7.48
2 1/2	65	2.875	73.0	0.276	7.01	2.323	59.0	7.67	11.41
3	80	3.500	88.9	0.300	7.62	2.900	73.7	10.26	15.27
3 1/2	90	4.000	101.6	0.318	8.08	3.364	85.4	12.52	18.64
4	100	4.500	114.3	0.337	8.56	3.826	97.2	15.00	22.32
5	125	5.563	141.3	0.375	9.53	4.813	122.3	20.80	30.97
6	150	6.625	168.3	0.432	10.97	5.761	146.3	28.60	42.56
8	200	8.625	219.1	0.500	12.70	7.625	193.7	43.43	64.64
10	250	10.750	273.0	0.594	15.09	9.562	242.9	64.49	95.98
12	300	12.750	323.8	0.688	17.48	11.374	288.9	88.71	132.05
14	350	14.000	355.6	0.750	19.05	12.500	317.5	106.23	158.11
16	400	16.000	406.4	0.844	21.44	14.312	363.5	136.74	203.54
18	450	18.000	457	0.938	23.83	16.124	409.5	171.08	254.57
20	500	20.000	508	1.031	26.19	17.938	455.6	209.06	311.19
22	550	22.000	559	1.125	28.58	19.750	501.7	251.05	373.85
24	600	24.000	610	1.219	30.96	21.562	547.7	296.86	442.11

Up to NPS 8 these walls are also the XS walls. From NPS 10, XS is still 0.500 in while Schedule 80 keeps growing.

Four traps that catch people out

Each of these is visible in the tables above once you know where to look.

NPS is a name, not a measurement

Up to NPS 12 the outside diameter is bigger than the number. NPS 2 is 2.375 in across, NPS 6 is 6.625 in and NPS 12 is 12.750 in. From NPS 14 up the name and the outside diameter match, so NPS 14 is 14.000 in and NPS 24 is 24.000 in.

You cannot tape a 4 inch pipe and expect to read 4. Measure the outside diameter and look it up: 114.3 mm is NPS 4.

Schedule 40 and STD match only up to NPS 10

At NPS 10 both are 0.365 in. At NPS 12, STD stays at 0.375 in while Schedule 40 goes to 0.406 in, and the gap widens: at NPS 24 STD is still 0.375 in and Schedule 40 is 0.688 in.

From NPS 12 up, STD and Schedule 40 are different pipe, so an order or a drawing needs to name the one it wants.

Schedule 80 and XS match only up to NPS 8

At NPS 8 both are 0.500 in. At NPS 10, XS stays at 0.500 in while Schedule 80 is 0.594 in, and at NPS 24 Schedule 80 is 1.219 in against 0.500 in for XS.

Stainless S schedules are not in this table

10S, 40S and 80S come from ASME B36.19M, which covers stainless pipe. Some walls match carbon steel and some do not. At NPS 14, Schedule 10 here is 0.250 in but 10S is 0.188 in, and at NPS 12 the 40S wall is 0.375 in where carbon Schedule 40 is 0.406 in.

For stainless, use the B36.19M table, not this one.

Work out inside diameter, weight and circumference yourself

The tables cover the standard walls. For anything else, these three sums get you there with a calculator.

Inside diameter

Outside diameter minus twice the wall. NPS 2 Schedule 40 is 2.375 in minus 2 x 0.154 in, which gives 2.067 in (52.5 mm).

Plain-end weight

lb/ft = 10.69 x (OD minus wall) x wall, with both in inches. kg/m = 0.02466 x (OD minus wall) x wall, with both in millimeters. NPS 2 Schedule 40 gives 10.69 x (2.375 minus 0.154) x 0.154 = 3.66 lb/ft.

Both land within 0.1 percent of the tables from NPS 2 up. For a length or a quantity, use the steel weight calculator.

Circumference

Wrap a tape around the pipe and divide by 3.1416 to get the outside diameter you look up. NPS 2 has a circumference of 7.46 in (189.4 mm). The circumference calculator does it either way.

Pipe offsets and pipe weight in Fabora Steel Tools

Pipe Offset in Fabora Pro works out travel, run and cut lengths for simple and rolling offsets, with 90 and 45 degree long radius elbow take-outs for NPS 1/2 to 12. Steel Weight is free and gives the weight of any length of pipe or tube. Fabora Steel Tools is on iPhone, Android and the web.

Download on the App Store Get it on Google Play Use it free in your browser

Pipe schedule FAQ

The questions people actually ask at the pipe rack

Short answers, using the same numbers as the tables above.

What is the difference between NPS and DN?

NPS is the inch-based name for a pipe size and DN is the metric name for the same pipe, so NPS 2 is DN 50 and NPS 4 is DN 100. Neither one is a measurement. From NPS 1 up, DN is roughly 25 times the NPS number, rounded to a standard figure, which is why NPS 1 1/2 is DN 40 and NPS 2 1/2 is DN 65.

What is the outside diameter of 2 inch pipe?

2 inch pipe (NPS 2, DN 50) has an outside diameter of 2.375 in (60.3 mm) in every schedule. The wall is what changes: 0.154 in (3.91 mm) for Schedule 40 and 0.218 in (5.54 mm) for Schedule 80.

What does pipe schedule mean?

A schedule number is a label that, together with the NPS, gives the wall thickness. The outside diameter stays the same for a given NPS, so a higher schedule means a thicker wall and a smaller bore. On 2 inch pipe the outside diameter is 2.375 in throughout, and the bore is 2.067 in at Schedule 40 and 1.939 in at Schedule 80.

How do you work out the inside diameter of pipe?

Take the outside diameter and subtract twice the wall. For 2 inch Schedule 40 that is 2.375 in minus 2 x 0.154 in, which is 2.067 in (52.5 mm). The Schedule 40 and Schedule 80 tables on this page give the inside diameter of every size.

Is Schedule 40 the same as standard weight (STD)?

Only up to NPS 10, where both are 0.365 in. From NPS 12 up, STD stays at 0.375 in while Schedule 40 gets thicker: 0.406 in at NPS 12 and 0.688 in at NPS 24. Say which one you mean on the drawing.

Is Schedule 80 the same as extra strong (XS)?

Only up to NPS 8, where both are 0.500 in. From NPS 10 up, XS stays at 0.500 in while Schedule 80 gets thicker: 0.594 in at NPS 10 and 1.219 in at NPS 24.

How much does Schedule 40 pipe weigh per foot?

Plain-end Schedule 40 weighs 3.66 lb/ft (5.44 kg/m) at NPS 2, 10.80 lb/ft (16.08 kg/m) at NPS 4 and 18.99 lb/ft (28.26 kg/m) at NPS 6. The Schedule 40 table above lists every size, and the steel weight calculator gives the weight of any length.

How do I find the NPS of a pipe I have measured?

Measure across the outside, or wrap a tape around it and divide by 3.1416, then match the result to the OD column. 60.3 mm is NPS 2, 114.3 mm is NPS 4 and 168.3 mm is NPS 6. Tube is different: it is sized by its true outside diameter, so a 2 inch tube measures 2.000 in while NPS 2 pipe measures 2.375 in.

What is the difference between ASME B36.10M and B36.19M?

B36.10M covers wrought carbon and alloy steel pipe, which is what this chart shows. B36.19M covers stainless steel pipe and uses the S schedules: 5S, 10S, 40S and 80S. Some walls match between the two and some do not, so do not read a stainless 10S wall from the Schedule 10 column.

Why do pipe schedule charts disagree with each other?

There are three usual reasons. Some sites convert inches to millimeters themselves, so NPS 10 shows as 273.1 mm where B36.10M tables print 273.0. Some weight tables use a slightly different constant, so 6 inch Schedule 40 is 18.97 lb/ft in one chart and 18.99 in another. And a few charts carry plain typing errors. The table at the bottom of this page lists every cell where the sources disagreed and the value used here.

Where these numbers come from

Every size, wall and weight on this page was read from published tables that reproduce ASME B36.10M, and each figure appears in at least two of them. The main ones are the B36.10 pages at wermac.org, the Edcon Steel line pipe chart (edconsteel.com.au, NPS 1/8 to 12), the pipe table at roymech.org, the Schedule 40 chart at hardhatengineer.com, and the charts at projectmaterials.com, pipeflowcalculations.com and engineeringtoolbox.com, with the Wikipedia nominal pipe size article as a further check.

Weights come from wermac.org and botopsteelpipe.com, which agree on every figure in both units, and the kg/m column also matches the Edcon Steel chart and ssmalloys.com. Inside diameters are worked out as outside diameter minus twice the wall, and they match the Arc-Zone table of pipe schedules for every size up to NPS 8.

Where the tables disagree, this page uses the value the B36.10M-based tables print, not one a site has converted or rebuilt itself, and lists the disagreement below instead of picking one quietly. This is a reference chart, not the standard. For pressure piping, procurement or anything where a wall thickness has to be right, check the current edition of ASME B36.10M. Checked against the published tables on November 3, 2026.

Cells where the published pipe tables disagree, and the value used here
Cell	What the tables say	Used here
NPS 1 1/2 XXS wall, mm	Wermac, Edcon Steel, Pipe Flow Calculations and one Project Materials chart print 10.15. Wikipedia, Engineering ToolBox and another Project Materials chart print 10.16, which is 0.400 in converted exactly.	10.15, as the B36.10M tables print it
NPS 3 1/2 XXS wall	Wikipedia, Project Materials and the metric Engineering ToolBox table show 0.636 in (16.15 mm). Wermac, Edcon Steel, Pipe Flow Calculations and the Engineering ToolBox wall chart show none.	not listed
NPS 10 and 12 XXS wall	Wikipedia and one Engineering ToolBox table leave it blank. Wermac, Edcon Steel, Project Materials and Pipe Flow Calculations print 1.000 in (25.40 mm).	1.000 in (25.40 mm)
NPS 1/8, 1/4 and 3/8 Schedule 160 and XXS	Wermac prints walls for these cells. Edcon Steel, Engineering ToolBox, Project Materials and Wikipedia show none for either schedule, and Roymech shows none for Schedule 160.	not listed
NPS 1/2 Schedule 160 wall	Engineering ToolBox prints 0.187 in (4.75 mm). Wermac, Edcon Steel, Roymech, Project Materials and Wikipedia print 0.188 in (4.78 mm).	0.188 in (4.78 mm)
NPS 6 Schedule 160 wall	Engineering ToolBox prints 0.718 in. Wermac, Edcon Steel, Roymech and Project Materials print 0.719 in (18.26 mm).	0.719 in (18.26 mm)
Large-size walls, e.g. Schedule 40 at NPS 14	Wikipedia shows 0.437 in (11.10 mm) and is a thousandth of an inch low on several other large sizes. One Pipe Flow Calculations table also shows 0.437 in. Wermac, Roymech, Hardhat Engineer and Project Materials print 0.438 in (11.13 mm).	0.438 in (11.13 mm), and the printed values on the other large sizes
Outside diameter in mm at NPS 10, 12, 18, 22 and 24	B36.10M tables print 273.0, 323.8, 457, 559 and 610. Exact conversions of the inch sizes are 273.05, 323.85, 457.2, 558.8 and 609.6, and some sites round those to 273.1 and 323.9.	273.0, 323.8, 457, 559 and 610, as printed
Weight in lb/ft, e.g. NPS 6 Schedule 40	Engineering ToolBox (which says it is based on ASTM A53), Pipe Flow Calculations and the Project Materials weight chart print 18.97, which is what a 10.68 constant gives. Wermac and Botop print 18.99, from the 10.69 constant. The 28.26 kg/m figure is the same in Wermac, Botop, Edcon Steel and ssmalloys.com.	18.99 lb/ft and 28.26 kg/m, as Wermac and Botop print them

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