Pipe Size Chart: NPS, DN, OD and Schedule 40 & 80 (Inch and mm)

Need the outside diameter of a 2 inch pipe, or the inside diameter of Schedule 80? This pipe size chart lists every nominal pipe size from ⅛ to 24 inches with its DN equivalent, outside diameter, wall thickness, inside diameter and weight for Schedule 40 and Schedule 80, in inches and millimetres, plus copper tube sizes. Download the full chart as a free PDF at the end.

Quick answer

A pipe’s nominal size (NPS) is not its actual diameter. Up to 12 inches the outside diameter is larger than the nominal size (a 1 inch pipe is 1.315 in / 33.4 mm OD); from 14 inches up the OD equals the nominal size. The schedule (40, 80) only changes the wall thickness and inside diameter.

Pipe size chart showing NPS, DN, outside diameter and Schedule 40 and 80 wall thickness for steel pipe

In this guide

Pipe size chart in inches
Pipe size chart in mm with weight
NPS, DN and OD explained
What pipe schedule means
PVC pipe sizes
Copper tube size chart
Download the PDF chart
FAQ

Pipe Size Chart (Inches): Schedule 40 and 80

NPS (in)	OD (in)	Sch 40 wall	Sch 40 ID	Sch 80 wall	Sch 80 ID
⅛	0.405	0.068	0.269	0.095	0.215
¼	0.540	0.088	0.364	0.119	0.302
⅜	0.675	0.091	0.493	0.126	0.423
½	0.840	0.109	0.622	0.147	0.546
¾	1.050	0.113	0.824	0.154	0.742
1	1.315	0.133	1.049	0.179	0.957
1¼	1.660	0.140	1.380	0.191	1.278
1½	1.900	0.145	1.610	0.200	1.500
2	2.375	0.154	2.067	0.218	1.939
2½	2.875	0.203	2.469	0.276	2.323
3	3.500	0.216	3.068	0.300	2.900
4	4.500	0.237	4.026	0.337	3.826
5	5.563	0.258	5.047	0.375	4.813
6	6.625	0.280	6.065	0.432	5.761
8	8.625	0.322	7.981	0.500	7.625
10	10.750	0.365	10.020	0.593	9.564
12	12.750	0.406	11.938	0.687	11.376
14	14.000	0.437	13.126	0.750	12.500
16	16.000	0.500	15.000	0.843	14.314
18	18.000	0.562	16.876	0.937	16.126
20	20.000	0.593	18.814	1.031	17.938
24	24.000	0.687	22.626	1.218	21.564

Steel pipe dimensions to ASME B36.10M. All values in inches.

Pipe Size Chart (mm) with DN and Weight

NPS	DN	OD (mm)	Sch 40 wall	Sch 40 ID	Sch 40 kg/m	Sch 80 wall	Sch 80 ID	Sch 80 kg/m
⅛	DN6	10.3	1.73	6.8	0.36	2.41	5.5	0.47
¼	DN8	13.7	2.24	9.2	0.63	3.02	7.7	0.80
⅜	DN10	17.1	2.31	12.5	0.85	3.20	10.7	1.10
½	DN15	21.3	2.77	15.8	1.27	3.73	13.9	1.62
¾	DN20	26.7	2.87	20.9	1.68	3.91	18.8	2.20
1	DN25	33.4	3.38	26.6	2.50	4.55	24.3	3.23
1¼	DN32	42.2	3.56	35.1	3.39	4.85	32.5	4.46
1½	DN40	48.3	3.68	40.9	4.05	5.08	38.1	5.41
2	DN50	60.3	3.91	52.5	5.44	5.54	49.3	7.48
2½	DN65	73.0	5.16	62.7	8.63	7.01	59.0	11.41
3	DN80	88.9	5.49	77.9	11.28	7.62	73.7	15.27
4	DN100	114.3	6.02	102.3	16.07	8.56	97.2	22.32
5	DN125	141.3	6.55	128.2	21.77	9.52	122.3	30.95
6	DN150	168.3	7.11	154.1	28.26	10.97	146.3	42.56
8	DN200	219.1	8.18	202.7	42.53	12.70	193.7	64.63
10	DN250	273.1	9.27	254.5	60.30	15.06	242.9	95.82
12	DN300	323.8	10.31	303.2	79.73	17.45	289.0	131.84
14	DN350	355.6	11.10	333.4	94.29	19.05	317.5	158.09
16	DN400	406.4	12.70	381.0	123.29	21.41	363.6	203.27
18	DN450	457.2	14.27	428.7	155.91	23.80	409.6	254.34
20	DN500	508.0	15.06	477.9	183.08	26.19	455.6	311.12
24	DN600	609.6	17.45	574.7	254.79	30.94	547.7	441.43

Wall and ID in mm. Weight is plain-end carbon steel: lb/ft = 10.69 × (OD − t) × t, converted to kg/m.

Look up any size and schedule

Interactive chart with Schedule 40, 80 and 160 in inches or millimetres.

Open the Pipe Schedule Reference →

NPS, DN and OD: Why a 1 Inch Pipe Is Not 1 Inch

Pipe sizes started as the approximate inside diameter of early iron pipe. When stronger steel allowed thinner walls, the outside diameter was kept the same so fittings still matched, and the inside diameter changed instead. The result is today’s system:

NPS (Nominal Pipe Size) is a name in inches, not a measurement.
OD (outside diameter) is fixed for each NPS, whatever the schedule. Up to NPS 12 it is larger than the nominal size; from NPS 14 it equals the nominal size.
DN (Diamètre Nominal) is the metric name used in ISO and EN standards: DN25 = NPS 1, DN50 = NPS 2, DN100 = NPS 4.
ID (inside diameter) = OD − 2 × wall thickness, and depends on the schedule.

Common mix-up on site

DN100 pipe is not 100 mm outside diameter: it is 114.3 mm OD. Always check the OD when ordering fittings, clamps, sleeves and insulation.

What Pipe Schedule Means

The schedule number sets the wall thickness for each size. Higher schedule = thicker wall = higher pressure rating and smaller bore. Schedule 40 is the everyday standard for water, fire and HVAC piping; Schedule 80 is used for higher pressure, threaded joints in larger sizes, and where corrosion allowance is needed. Up to NPS 10, Schedule 40 is the same as the older STD (standard weight) class, and up to NPS 8 Schedule 80 matches XS (extra strong).

PVC Pipe Sizes

PVC Schedule 40 and Schedule 80 pressure pipe (ASTM D1785) is made to the same outside diameters as steel pipe, and its minimum wall thicknesses follow the same schedule table. That is why the chart above also works as a PVC pipe size chart for Schedule 40 and 80. Metric PVC and uPVC pipe (ISO 1452, EN 1401 drainage) is different: it is named by its actual outside diameter in mm, for example 110 mm or 160 mm, with the wall set by the pressure class.

Copper Tube Size Chart

Copper water tube (ASTM B88) uses a different rule: the outside diameter is the nominal size plus ⅛ inch. Type K has the thickest wall, Type L is the usual choice for domestic water, and Type M is the thinnest.

Nominal (in)	OD (in)	OD (mm)	Type K wall	Type L wall	Type M wall
½	0.625	15.88	0.049	0.040	0.028
¾	0.875	22.22	0.065	0.045	0.032
1	1.125	28.57	0.065	0.050	0.035
1¼	1.375	34.92	0.065	0.055	0.042
1½	1.625	41.27	0.072	0.060	0.049
2	2.125	53.97	0.083	0.070	0.058
2½	2.625	66.67	0.095	0.080	0.065
3	3.125	79.38	0.109	0.090	0.072
4	4.125	104.77	0.134	0.110	0.095

Wall thickness in inches.

Download the Pipe Size Chart PDF

The free PDF has the full steel chart (inches and mm, Schedule 40 and 80 with weights), the copper tube chart and an NPS to DN table, on two printable A4 pages.

Checking…

Drafting pipe sections? The DWG has every size from NPS ⅛ to 24 as a true-scale block (outside and inside circles, in mm) for Schedule 40 and 80, named MB_PIPE_DN50_SCH40 and so on.

Checking…

Frequently Asked Questions

What is the outside diameter of a 1 inch pipe?

1.315 inches (33.4 mm) for steel and PVC Schedule 40 or 80. The nominal size of 1 inch is a name, not a measurement.

What is the difference between NPS and DN?

They are two names for the same pipe size. NPS is the inch-based name used in North America (NPS 2), DN is the metric name used in ISO and EN standards (DN50). The pipe has the same outside diameter.

What is the difference between Schedule 40 and Schedule 80?

Schedule 80 has a thicker wall than Schedule 40 for the same size, so it handles higher pressure but has a smaller inside diameter. The outside diameter is the same, so both use the same fittings.

Are PVC and steel pipe sizes the same?

For Schedule 40 and 80 PVC pressure pipe to ASTM D1785, yes: the outside diameters and minimum walls match the steel pipe schedule. Metric PVC pipe is named by its outside diameter in mm and does not follow the steel chart.

When does pipe OD equal the nominal size?

From NPS 14 upwards. A 14 inch pipe has a 14.000 inch outside diameter, while every size up to 12 inches has an OD larger than its nominal size.

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Written by Faisal, MEP engineer with 16+ years in building services design. Dimensions per ASME B36.10M and ASTM B88; confirm against the manufacturer’s data for final design.