What is the actual inside diameter of 1 inch Schedule 40 pipe?

1 in Schedule 40 steel pipe has a 1.315 in outside diameter, 0.133 in wall and 1.049 in inside diameter.

What is the difference between Schedule 40 and Schedule 80?

Schedule 80 has a thicker wall at the same outside diameter, so it carries higher pressure but has a smaller bore and more pressure drop at the same flow.

Can PVC be used for compressed air?

No. PVC is not rated for compressed air and can shatter; use steel, copper, stainless or an air-rated aluminum system.

Pipe Properties Chart — OD, ID, Wall, Pressure

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Formula

ID = OD − 2·wall · Area = π(ID/2)² · Weight/ft = ρ·(A_metal)·12

Look up dimensions, weight, working pressure, internal volume and rough CFM capacity for the piping materials common in compressed-air systems.

Material / schedule

Nominal size

Line pressure

psig

Run length (for CFM capacity)

Outside diameter

1.660in

42.2 mm

Inside diameter

1.380in

35.1 mm

Wall thickness

0.140in

3.56 mm

Cross-section

1.496in²

965 mm²

Weight

2.28lb/ft

3.39 kg/m

Internal volume

0.0777gal/ft

0.965 L/m

Pressure check

Rated 700 psi · line 125 psi · safety factor 5.6×

Compressed-air code typically requires 4× safety factor on burst pressure.

Approx. flow capacity

11cfm

At 125 psig over 100 ft, ≈ 2 psi/100 ft drop target

Material notes

Standard compressed-air header material. NPT threaded or welded.

Full size chart — Carbon steel — Sch 40 (A53/A106)

NPS	OD (in)	Wall	ID	Area (in²)	lb/ft	gal/ft	WP psi
1/8"	0.405	0.068	0.269	0.057	0.25	0.0030	700
1/4"	0.540	0.088	0.364	0.104	0.43	0.0054	700
3/8"	0.675	0.091	0.493	0.191	0.57	0.0099	700
1/2"	0.840	0.109	0.622	0.304	0.85	0.0158	700
3/4"	1.050	0.113	0.824	0.533	1.13	0.0277	700
1"	1.315	0.133	1.049	0.864	1.68	0.0449	700
1-1/4"	1.660	0.140	1.380	1.496	2.28	0.0777	700
1-1/2"	1.900	0.145	1.610	2.036	2.72	0.1058	700
2"	2.375	0.154	2.067	3.356	3.66	0.1743	700
2-1/2"	2.875	0.203	2.469	4.788	5.80	0.2487	700
3"	3.500	0.216	3.068	7.393	7.58	0.3840	700
4"	4.500	0.237	4.026	12.730	10.80	0.6613	700
6"	6.625	0.280	6.065	28.890	18.99	1.5008	700
8"	8.625	0.322	7.981	50.027	28.58	2.5988	700

How to use this calculator

Find outside diameter, wall thickness, inside diameter and internal volume for standard pipe sizes.

Select the pipe material and nominal size.
Select the schedule or wall class.
Read outside diameter, wall thickness and inside diameter.
Use the internal area and volume figures for velocity or storage calculations.

Frequently asked questions

What is the actual inside diameter of 1 inch Schedule 40 pipe?: 1 in Schedule 40 steel pipe has a 1.315 in outside diameter, 0.133 in wall and 1.049 in inside diameter.
What is the difference between Schedule 40 and Schedule 80?: Schedule 80 has a thicker wall at the same outside diameter, so it carries higher pressure but has a smaller bore and more pressure drop at the same flow.
Can PVC be used for compressed air?: No. PVC is not rated for compressed air and can shatter; use steel, copper, stainless or an air-rated aluminum system.