A106 Pipe Dimensions, Sizes & Schedule Chart

A106 pipe dimensions are commonly specified by nominal pipe size (NPS), outside diameter (OD), wall thickness, and pipe Schedule. The tables below provide a practical reference for common A106 pipe sizes, including NPS, DN, outside diameter, and standard wall thicknesses for Schedule 10, 40, 80, and 160.

For quick size conversion, the charts show outside diameter in both millimeters and inches, while DN provides the corresponding metric nominal designation. Because NPS is a nominal designation rather than a direct measurement of the pipe outside diameter, the actual OD should be checked from the applicable dimensional standard.

A106 Pipe Size Chart

The following A106 pipe size chart covers common NPS sizes from 1/2 inch to 12 inches. It shows the relationship between NPS, DN, and actual outside diameter, making it useful when comparing inch and metric pipe dimensions.

NPS	DN	OD (mm)	OD (in.)
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
3-1/2	90	101.6	4.000
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	323.9	12.750

The NPS value is the nominal pipe size in inches, while DN is the corresponding nominal metric designation. Neither NPS nor DN represents the actual measured outside diameter. For example, NPS 2 corresponds to DN 50, but its actual OD is 60.3 mm (2.375 in.).

These dimensions are used across A106 seamless carbon steel pipe products regardless of whether the pipe is supplied in Schedule 10, Schedule 40, Schedule 80, or another applicable Schedule. The Schedule changes the wall thickness rather than the standard OD for a given NPS.

A106 Pipe Dimensions by Schedule

For a given NPS, the standard outside diameter remains fixed while the wall thickness varies by Schedule. This is the key principle for reading an A106 pipe schedule chart: NPS identifies the nominal size, while Schedule identifies the standard wall thickness.

NPS	DN	OD (mm)	Sch 10 (mm)	Sch 40 (mm)	Sch 80 (mm)	Sch 160 (mm)
1/2	15	21.3	2.11	2.77	3.73	4.78
3/4	20	26.7	2.11	2.87	3.91	5.56
1	25	33.4	2.77	3.38	4.55	6.35
1-1/4	32	42.2	2.77	3.56	4.85	6.35
1-1/2	40	48.3	2.77	3.68	5.08	7.14
2	50	60.3	2.77	3.91	5.54	8.74
2-1/2	65	73.0	3.05	5.16	7.01	9.53
3	80	88.9	3.05	5.49	7.62	11.13
3-1/2	90	101.6	3.05	5.74	8.08	—
4	100	114.3	3.05	6.02	8.56	13.49
5	125	141.3	3.40	6.55	9.52	15.88
6	150	168.3	3.40	7.11	10.97	18.26
8	200	219.1	3.76	8.18	12.70	20.62
10	250	273.0	4.19	9.27	15.09	25.40
12	300	323.9	4.57	9.53	17.48	28.58

The dimensional system above follows ASME B36.10M, which specifies dimensions for welded and seamless wrought steel pipe. Not every Schedule is available for every NPS, so the applicable dimensional range should be confirmed for the required pipe size.

For the same NPS, a higher Schedule generally means a thicker wall. For example, NPS 2 has an OD of 60.3 mm for Schedule 10, 40, 80, and 160, while the wall thickness increases from 2.77 mm to 8.74 mm.

A106 Schedule 40 therefore refers to A106 pipe supplied with the standard Schedule 40 wall thickness for the selected NPS. For example, NPS 2 Schedule 40 has an OD of 60.3 mm and a wall thickness of 3.91 mm. The same dimensional principle applies to ASTM A106 Gr B Schedule 40: the grade defines the material requirements, while NPS and Schedule determine the pipe dimensions.

For customers looking for ASTM A106 seamless carbon steel pipe in specific sizes and Schedules, see our A106 Grade B Steel Pipe product page for available grades, dimensions, and supply options.

How A106 Pipe Dimensions Are Specified

An A106 pipe size is normally described using several related dimensions.

NPS — Nominal Pipe Size

NPS (Nominal Pipe Size) is the standard nominal designation used for pipe size in inches. It does not directly represent the measured outside diameter.

For example:

• NPS 1 = nominal 1-inch pipe size, actual OD 33.4 mm
• NPS 2 = nominal 2-inch pipe size, actual OD 60.3 mm
• NPS 4 = nominal 4-inch pipe size, actual OD 114.3 mm
• NPS 6 = nominal 6-inch pipe size, actual OD 168.3 mm

DN — Nominal Diameter

DN is the metric nominal designation corresponding to NPS. Common equivalents include NPS 1 = DN 25, NPS 2 = DN 50, NPS 4 = DN 100, NPS 6 = DN 150, and NPS 12 = DN 300.

DN is also a nominal designation and should not be treated as the actual pipe OD.

Outside Diameter (OD)

Outside diameter (OD) is the specified external diameter of the pipe. Unlike NPS, OD is an actual dimensional value used for engineering, fabrication, fittings, and installation.

For a given NPS, the standard OD generally remains unchanged when the Schedule changes. For example, both NPS 2 Schedule 40 and NPS 2 Schedule 80 have an OD of 60.3 mm.

Wall Thickness

Wall thickness is the thickness of the pipe wall and is one of the most important A106 dimensional parameters when selecting a Schedule.

For the same NPS, wall thickness increases as the Schedule increases. For NPS 2:

• Schedule 10: 2.77 mm
• Schedule 40: 3.91 mm
• Schedule 80: 5.54 mm
• Schedule 160: 8.74 mm

Wall thickness affects the internal diameter, pipe weight, pressure capability, and suitability for a particular application.

Pipe Schedule

Pipe Schedule is the standardized designation used to identify pipe wall thickness. Common schedules include Schedule 10, 20, 30, 40, 60, 80, 100, 120, 140, and 160, although not every Schedule is available for every NPS.

For this reason, an A106 pipe size is normally specified using a combination such as NPS 2 Sch 40, rather than by nominal size alone.

A106 Pipe Dimensions FAQ

What are the standard A106 pipe sizes?

Common A106 pipe sizes include NPS 1/2 through 12 inches and larger sizes depending on the application and supply requirements. The actual wall thickness depends on the selected Schedule.

What is the OD of a 2-inch A106 pipe?

A 2-inch A106 pipe has a standard outside diameter of 60.3 mm (2.375 inches). The outside diameter remains the same across common Schedule options, while the wall thickness changes.

What is the wall thickness of A106 Schedule 40 pipe?

The A106 Schedule 40 wall thickness depends on the NPS. For example, NPS 2 Schedule 40 has a wall thickness of 3.91 mm, while NPS 4 Schedule 40 has a wall thickness of 6.02 mm.

What is A106 Schedule 40?

A106 Schedule 40 refers to ASTM A106 pipe with the standard Schedule 40 wall thickness for the specified NPS. The required wall thickness therefore varies with pipe size.

Does a higher Schedule mean a larger pipe diameter?

No. For a given NPS, changing the Schedule generally changes the wall thickness, not the outside diameter. A higher Schedule normally means a thicker pipe wall.

Are A106 pipe dimensions the same for different Grades?

The dimensional system is based on NPS and Schedule, rather than the A106 Grade. Therefore, A106 Gr A, Gr B, and Gr C do not require separate dimensional charts solely because of the Grade.