Pipe Dimension Chart

Why the outside diameter does not change with schedule, why STD stops matching Schedule 40 above NPS 10, and why the S series is not the plain series is all explained in thepipe schedule, NPS and wall thickness guide. If you are here to look a number up rather than to work out which number you need, this pipe dimension chart is below. Ranges are underpipes and tubes.

NPS to DN and Outside Diameter

NPS	DN	OD, mm	OD, in
1/8	6	10.3	0.405
1/4	8	13.7	0.540
3/8	10	17.1	0.675
1/2	15	21.3	0.840
3/4	20	26.7	1.050
1	25	33.4	1.315
1 1/4	32	42.2	1.660
1 1/2	40	48.3	1.900
2	50	60.3	2.375
2 1/2	65	73.0	2.875
3	80	88.9	3.500
4	100	114.3	4.500
5	125	141.3	5.563
6	150	168.3	6.625
8	200	219.1	8.625
10	250	273.0	10.750
12	300	323.8	12.750
14	350	355.6	14.000
16	400	406.4	16.000
18	450	457.0	18.000
20	500	508.0	20.000
24	600	610.0	24.000

From NPS 14 upward the outside diameter equals the nominal size in inches. Below that it does not.

Wall Thickness by Schedule, mm

NPS	Sch 40	Sch 80	Sch 160
1/2	2.77	3.73	4.78
3/4	2.87	3.91	5.56
1	3.38	4.55	6.35
1 1/2	3.68	5.08	7.14
2	3.91	5.54	8.74
3	5.49	7.62	11.13
4	6.02	8.56	13.49
6	7.11	10.97	18.26
8	8.18	12.70	23.01
10	9.27	15.09	28.58
12	10.31	17.48	33.32
14	11.13	19.05	35.71
16	12.70	21.44	40.49
18	14.27	23.83	45.24
20	15.09	26.19	50.01
24	17.48	30.96	59.54

Bore by Schedule, mm

Bore equals outside diameter minus twice the wall. This is the dimension a hydraulic calculation uses, and it is the one that changes when a schedule is substituted:

NPS	Sch 40 bore	Sch 80 bore	Sch 160 bore
1/2	15.76	13.84	11.74
3/4	20.96	18.88	15.58
1	26.64	24.30	20.70
1 1/2	40.94	38.14	34.02
2	52.48	49.22	42.82
3	77.92	73.66	66.64
4	102.26	97.18	87.32
6	154.08	146.36	131.78
8	202.74	193.70	173.08
10	254.46	242.82	215.84
12	303.18	288.84	257.16
14	333.34	317.50	284.18
16	381.00	363.52	325.42
18	428.46	409.34	366.52
20	477.82	455.62	407.98
24	575.04	548.08	490.92

STD, XS and XXS

Designation	Relationship
STD, standard	Equals Sch 40 up to NPS 10. From NPS 12 upward, a constant 9.53 mm
XS, extra strong	Equals Sch 80 up to NPS 8. From NPS 10 upward, a constant 12.70 mm
XXS, double extra strong	No schedule equivalent across the range. Take from the table

At NPS 16, STD gives 9.53 mm against 12.70 mm for Sch 40, a difference of about a quarter of the wall. This is the most common large bore ordering error.

The S Series, ASME B36.19M

Stainless and alloy pipe uses a parallel series with an S suffix:

NPS	5S	10S	40S	80S
1/2	1.65	2.11	2.77	3.73
3/4	1.65	2.11	2.87	3.91
1	1.65	2.77	3.38	4.55
1 1/2	1.65	2.77	3.68	5.08
2	1.65	2.77	3.91	5.54
3	2.11	3.05	5.49	7.62
4	2.11	3.05	6.02	8.56
6	2.77	3.40	7.11	10.97
8	2.77	3.76	8.18	12.70
10	3.40	4.19	9.27	12.70
12	3.96	4.57	9.53	12.70

Note that from NPS 10 upward 40S and 80S stop matching Sch 40 and Sch 80. The thin 5S and 10S walls have no carbon steel equivalent, and they are thin enough that the welding procedure matters more than it does on a carbon steel wall. Seestainless steel buttweld fittings.

Where Other Dimensions Come From

Pipe dimensions are only one family. The others are in their own standards:

Component	Dimensional standard
Buttweld fittings	ASME B16.9, ordered by schedule to match the pipe
Socket weld and threaded fittings	ASME B16.11, ordered by class
Flanges NPS 1/2 to 24	ASME B16.5, by class and facing
Flanges NPS 26 and above	ASME B16.47, Series A or Series B, which do not mate
Orifice flanges	ASME B16.36
Line blanks and spectacle blinds	ASME B16.48
Gaskets	ASME B16.20
Weld end preparation	ASME B16.25
High yield fittings	MSS SP-75
Branch outlets	MSS SP-97

Which standard governs which part of a callout is in theASTM vs ASME guide.

Related Calculations

Weight:pipe weight chart andsteel weight calculator
Pressure and wall:pipe pressure rating chart
Flange ratings:flange pressure and temperature rating guide

Pipe Dimensions FAQ

Does the outside diameter change with schedule?

No. For a given NPS the outside diameter is fixed, so changing schedule changes the bore and the flow area.

Where does NPS stop differing from the inch size?

From NPS 14 upward the outside diameter equals the nominal size in inches. Below that it does not, so NPS 2 is 60.3 mm rather than 50.8 mm.

Is STD the same as Schedule 40 at NPS 16?

No. From NPS 12 upward STD is a constant 9.53 mm, against 12.70 mm for Sch 40 at NPS 16.

Do 40S and 80S always match Sch 40 and Sch 80?

No. The correspondence holds at smaller sizes and breaks from around NPS 10 upward, so the S series has to be read from its own table.

Why does bore matter when a schedule is substituted?

Because the bore is what a hydraulic calculation uses, so a schedule change alters the flow area even though everything still bolts together.

Where do fitting and flange dimensions come from?

Their own standards: ASME B16.9 for buttweld fittings, B16.11 for forged, B16.5 and B16.47 for flanges, and MSS SP-75 and SP-97 for items outside the ASME series.

Applying This to an Enquiry

When sending a line list, give the schedule for pipe and the schedule for the buttweld fittings separately. They are two line items describing one joint, and the wall mismatch between them is the most common dimensional error on a piping order.

Quotations are available in USD, OMR, AED, SAR, QAR, KWD and BHD, on EXW, FOB, CFR or CIF terms, with EN 10204 3.1 certificates as standard and 3.2 on request. Lead time is confirmed at quotation.

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Pipe Dimensions: Reference Tables