Schedule 40 carbon steel pipe size chart and dimensions

What Is Schedule 40 CS Pipe?

Schedule 40 carbon steel pipe is a carbon steel pipe manufactured with a standardized wall thickness classification. The SCH number indicates the relationship between pipe diameter and wall thickness rather than the actual thickness value.
For example:
A 2 inch SCH 40 carbon steel pipe has a wall thickness of approximately 3.91 mm
A 12 inch SCH 40 carbon steel pipe has a wall thickness of approximately 10.31 mm
Although both pipes are SCH 40, their actual wall thicknesses are different because they have different outside diameters.
Schedule 40 dimensions are mainly based on the requirements of:
ASME B36.10M for carbon steel pipe dimensions
ASTM A53 for general carbon steel pipe
ASTM A106 for high-temperature applications
API 5L for oil and gas pipeline applications
Because of its moderate wall thickness and wide availability, SCH 40 carbon steel pipe has become a standard choice for many medium-pressure piping systems.

Schedule 40 Carbon Steel Pipe size chart, dimensions, wall thickness and weight

The dimensions of SCH 40 carbon steel pipe are determined by the nominal pipe size (NPS). The main parameters include:
Outside Diameter (OD)
Inside Diameter (ID)
Wall Thickness
Weight per unit length
The following table shows common SCH 40 carbon steel pipe dimensions based on standard pipe sizing

Nominal size [inches]	Outside diameter [inches]	Outside diameter [mm]	Wall thickness [inches]	Wall thickness [mm]	Weight [lb/ft]	Weight [kg/m]
1/8 inches	0.405 inches	10.3 MM	0.068 inches	1.73 MM	0.24 lb/ft	0.37 kg/m
1/4 inches	0.540 inches	13.7 MM	0.088 inches	2.24 MM	0.42 lb/ft	0.84 kg/m
1/2 inches	0.840 inches	21.3 MM	0.109 inches	2.77 MM	0.85 lb/ft	1.27 kg/m
3/4 inches	1.050 inches	26.7 MM	0.113 inches	2.87 MM	1.13 lb/ft	1.69 kg/m
1 inches	1.315 inches	33.4 MM	0.133 inches	3.38 MM	1.68 lb/ft	2.50 kg/m
1 1/4 inches	1.660 inches	42.2 MM	0.140 inches	3.56 MM	2.27 lb/ft	3.39 kg/m
1 1/2 inches	1.900 inches	48.3 MM	0.145 inches	3.68 MM	2.72 lb/ft	4.05 kg/m
2 inches	2.375 inches	60.3 MM	0.154 inches	3.91 MM	3.65 lb/ft	5.44 kg/m
2 1/2 inches	2.875 inches	73.0 MM	0.203 inches	5.16 MM	5.79 lb/ft	8.63 kg/m
3 inches	3.500 inches	88.9 MM	0.216 inches	5.49 MM	7.58 lb/ft	11.29 kg/m
3 1/2 inches	4.000 inches	101.6 MM	0.226 inches	5.74 MM	9.11 lb/ft	13.57 kg/m
4 inches	4.500 inches	114.3 MM	0.237 inches	6.02 MM	10.79 lb/ft	16.07 kg/m
5 inches	5.563 inches	141.3 MM	0.258 inches	6.55 MM	14.62 lb/ft	21.77 kg/m
6 inches	6.625 inches	168.3 MM	0.280 inches	7.11 MM	18.97 lb/ft	28.26 kg/m
8 inches	8.625 inches	219.1 MM	0.322 inches	8.18 MM	28.55 lb/ft	42.55 kg/m
10 inches	10.750 inches	273.0 MM	0.365 inches	9.27 MM	40.48 lb/ft	60.31 kg/m
12 inches	12.750 inches	323.8 MM	0.406 inches	10.31 MM	53.52 lb/ft	79.73 kg/m
14 inches	14 inches	355.6 MM	0.375 inches	11.13 MM	54.57 lb/ft	94.55 kg/m
16 inches	16 inches	406.4 MM	0.500 inches	12.70 MM	82.77 lb/ft	123.30 kg/m
18 inches	18 inches	457.0 MM	0.562 inches	14.27 MM	104.67 lb/ft	155.80 kg/m
20 inches	20 inches	508.0 MM	0.594 inches	15.09 MM	123.11 lb/ft	183.42 kg/m
24 inches	24 inches	610.0 MM	0.688 inches	17.48 MM	171.29 lb/ft	255.41 kg/m
32 inches	32 inches	813.0 MM	0.688 inches	17.48 MM	230.08 lb/ft	342.91 kg/m

Note: Dimensions may vary slightly depending on manufacturing standard and tolerance requirements.

Multiple material options for Schedule 40 carbon steel pipes

In addition, API 5L Gr. B carbon steel and galvanized iron materials are also commonly used in the production of No. 40 pipes. These materials have good corrosion resistance and wear resistance, allowing No. 40 carbon steel pipes to maintain stable performance under harsh environmental conditions.

How to Read a Schedule 40 Pipe Size Chart ?

Many buyers confuse pipe size with actual diameter. In steel pipe terminology:
NPS Does Not Equal Outside Diameter
For example:
A 2 inch SCH 40 pipe:
Nominal size: 2 inches
Outside diameter: 60.3 mm
Inside diameter: about 52.5 mm
Wall thickness: 3.91 mm

The “2 inch” designation is only a nominal reference size, not the measured diameter.

Wall Thickness Changes with Pipe Diameter

A common misunderstanding is that all SCH 40 pipes have the same wall thickness.
In reality:
Small diameter SCH 40 pipes have thinner walls
Large diameter SCH 40 pipes require thicker walls to maintain strength

Pipe Size	Wall Thickness
1/2" SCH 40	2.77 mm
4" SCH 40	6.02 mm
12" SCH 40	10.31 mm

This design allows SCH 40 pipes to maintain a practical balance between pressure resistance and material cost.

SCH 40 vs SCH 80 Carbon Steel Pipe

The main difference between SCH 40 and SCH 80 carbon steel pipe is wall thickness.

Item	SCH 40	SCH 80
Wall Thickness	Standard	Thicker
Weight	Lower	Higher
Pressure Capacity	Medium	Higher
Cost	More economical	More expensive
Common Use	General piping systems	Higher-pressure applications

SCH 40 is usually selected when operating conditions are moderate and cost efficiency is important. SCH 80 is preferred when additional strength and pressure resistance are required.

How to Choose the Right Schedule 40 Carbon Steel Pipe ？

When selecting SCH 40 carbon steel pipe, engineers should consider more than just pipe size.

1. Operating Pressure
Confirm that the pipe pressure rating meets the system design requirements.

2. Temperature Conditions
High-temperature applications may require materials such as ASTM A106 rather than general ASTM A53 pipe.

3. Corrosion Environment
For outdoor or corrosive environments, additional protection such as galvanizing, coating, or corrosion allowance may be required.

4. Manufacturing Standard
Always confirm whether the project requires ASTM, API, or other international standards.

Summary

Schedule 40 carbon steel pipes is a widely used pipe specification with moderate wall thickness, strong pressure bearing capacity, and can be treated with corrosion protection through a variety of processes. Whether it is used for building frames, industrial pipelines, or for conveying liquids or gases, No. 40 carbon steel pipes can become an indispensable and important pipe material in engineering with its stable performance and wide range of material options.

Read more

Schedule 40 Pipe Pressure Rating Chart and Guide