Schedule 40 Aluminum Pipe

Schedule 40 aluminum pipe is a widely used aluminum piping product defined by the NPS pipe sizing system and Schedule 40 wall thickness. It combines the low weight and corrosion resistance of aluminum with a standardized pipe dimension system.

Common grades include 6061-T6 aluminum, which offers a useful balance of strength, corrosion resistance, machinability, and weldability. Schedule 40 aluminum pipe is available in multiple nominal pipe sizes, with the outside diameter fixed by the NPS size and the wall thickness determined by the schedule.

What Is Schedule 40 Aluminum Pipe?

Schedule 40 aluminum pipe is a round aluminum pipe manufactured to a standard nominal pipe size and Schedule 40 wall designation.Unlike a simple aluminum tube, Schedule 40 aluminum pipe follows a nominal pipe size system. The nominal size does not directly equal the actual outside diameter. For example, 1-inch Schedule 40 aluminum pipe has a 1.315-inch outside diameter and a 0.133-inch wall thickness.
The term Schedule 40 does not mean that the wall thickness is 0.040 inch. Instead, Schedule 40 identifies a specific wall thickness for each nominal pipe size.

As the nominal pipe size increases, the outside diameter and Schedule 40 wall thickness also change.

Schedule 40 Aluminum Pipe Dimensions

The table below shows the standard dimensions of Schedule 40 aluminum pipe, including outside diameter (OD), inside diameter (ID), wall thickness, and weight per foot.
Schedule 40 aluminum pipe dimensions are based on the IPS (Iron Pipe Size) / NPS (Nominal Pipe Size) system. The outside diameter remains standardized, while the wall thickness increases with larger pipe sizes.
Common aluminum alloys include 6061-T6 and 6063-T6, which are widely used for structural applications, marine components, machinery frames, and general fabrication.

NPS / IPS (inch)	Outside Diameter (OD)	Inside Diameter (ID)	Wall Thickness	Weight (lb/ft)
1/8"	0.405"	0.269"	0.068"	0.085
1/4"	0.540"	0.364"	0.088"	0.147
3/8"	0.675"	0.493"	0.091"	0.196
1/2"	0.840"	0.622"	0.109"	0.294
3/4"	1.050"	0.824"	0.113"	0.391
1"	1.315"	1.049"	0.133"	0.581
1-1/4"	1.660"	1.380"	0.140"	0.786
1-1/2"	1.900"	1.610"	0.145"	0.94
2"	2.375"	2.067"	0.154"	1.26
2-1/2"	2.875"	2.469"	0.203"	2
3"	3.500"	3.068"	0.216"	2.62
3-1/2"	4.000"	3.548"	0.226"	3.15
4"	4.500"	4.026"	0.237"	3.73
5"	5.563"	5.047"	0.258"	5.06
6"	6.625"	6.065"	0.280"	6.56
8"	8.625"	7.981"	0.322"	9.88
10"	10.750"	10.020"	0.365"	14
12"	12.750"	12.000"	0.375"	17.14

Note: Dimensions may vary slightly depending on alloy, manufacturing method, and applicable ASTM specification. Always confirm final dimensions with the manufacturer's technical data before fabrication.

How to Read a Schedule 40 Aluminum Pipe Size Chart?

A Schedule 40 aluminum pipe size chart contains several important measurements:

Outside Diameter (OD)
The outside diameter is the actual measurement across the outside surface of the pipe.
For example:
1 inch Schedule 40 aluminum pipe has an OD of 1.315 inches
2 inch Schedule 40 aluminum pipe has an OD of 2.375 inches
4 inch Schedule 40 aluminum pipe has an OD of 4.500 inches
The OD is important when selecting fittings, clamps, supports, and mechanical connections.

Inside Diameter (ID)
The inside diameter determines the available internal space for:
Fluid flow
Gas transmission
Wiring
Mechanical components
The ID is calculated by:
ID = OD − (2 × Wall Thickness)
A 4 inch Schedule 40 aluminum pipe:
OD: 4.500"
Wall thickness: 0.237"
ID: approximately 4.026"

Wall Thickness
The wall thickness of Schedule 40 aluminum pipe is not fixed.
It changes depending on the nominal pipe size.

Size	Wall Thickness
1"	0.133"
2"	0.154"
4"	0.237"
6"	0.280"
10"	0.365"

6061-T6 Schedule 40 Aluminum Pipe

6061-T6 aluminum pipe is one of the most common material choices for Schedule 40 aluminum pipe.
The 6061 alloy belongs to the 6000 series of aluminum alloys. The T6 temper provides higher strength than the annealed condition.

Typical advantages include:
Good strength-to-weight ratio
Good corrosion resistance
Good machinability
Good weldability
Relatively low density
Good availability
Suitable performance for many structural applications
Commercial 6061-T6 Schedule 40 pipe is available in both extruded and seamless forms. Some seamless products are supplied to ASTM B241, while extruded products may be listed to ASTM B429, depending on the product and manufacturing method.

6061-T6 vs 6063 Aluminum Pipe

6061 and 6063 are both widely used aluminum alloys, but they are not interchangeable in every application.

Property	6061-T6	6063
Strength	Higher	Lower
Corrosion resistance	Good	Very good
Extrudability	Good	Excellent
Machinability	Good	Moderate
Structural applications	Excellent choice	Suitable for lighter-duty uses
Appearance	Good	Excellent
Typical uses	Structural pipe, marine, machinery	Railings, architectural products, decorative applications

For load-bearing applications, 6061-T6 is often preferred when higher strength is required.

ASTM Standards for Schedule 40 Aluminum Pipe

The material specification should always be checked separately from the Schedule designation.
For example, a product may be identified as:
6061-T6 aluminum pipe, Schedule 40, ASTM B241
ASTM B241 covers seamless aluminum and aluminum-alloy pipe and seamless extruded tube.
Other aluminum pipe products may use different specifications depending on their manufacturing process and intended application.
A useful purchasing description should therefore include:
Alloy + Temper + NPS + Schedule + Manufacturing Method + Applicable ASTM Specification

Schedule 40 vs Schedule 80 Aluminum Pipe

The main difference between Schedule 40 and Schedule 80 is wall thickness.
For the same NPS size, the outside diameter normally remains the same while Schedule 80 has a thicker wall.

NPS	SCH 40 Wall	SCH 80 Wall
1/2"	0.109"	0.147"
1"	0.133"	0.179"
2"	0.154"	0.218"
3"	0.216"	0.300"
4"	0.237"	0.337"
6"	0.280"	0.432"
8"	0.322"	0.500"
10"	0.365"	0.593"
12"	0.375"*	0.687"*

Schedule 80 therefore provides a larger wall thickness and smaller internal diameter at the same nominal size.

Schedule 40 Aluminum Pipe Weight

Weight is often important when designing lightweight structures.
For example:
1" Schedule 40 aluminum pipe: about 0.581 lb/ft
1-1/2": about 0.940 lb/ft
2": about 1.260 lb/ft
4": about 3.730 lb/ft
6": about 6.560 lb/ft
8": about 9.880 lb/ft
10": about 14.000 lb/ft
12": about 17.140 lb/ft
Actual product weight can vary with alloy, manufacturing tolerance, and product specification.
For a long structural assembly, this difference can become significant.
Replacing a steel component with aluminum may reduce handling weight substantially. However, the design must still satisfy strength and stiffness requirements.

Is Schedule 40 Aluminum Pipe Good for High Pressure?

Schedule 40 does not by itself provide a universal pressure rating for aluminum pipe.
This is an important distinction.
A pressure rating depends on more than pipe schedule. Important factors include:
Aluminum alloy
Temper
OD
Wall thickness
Operating temperature
Corrosion allowance
Welded or seamless construction
Joint efficiency
Threaded or welded connections
Applicable pressure design code
For example, a 6061-T6 Schedule 40 pipe and another aluminum alloy with the same nominal dimensions may not have the same allowable working pressure.
Therefore, do not select an aluminum pipe for a pressure system using the Schedule number alone.
For pressure applications, consult the applicable design code and obtain the manufacturer's allowable pressure data or perform an engineering calculation.

FAQ

What is Schedule 40 aluminum pipe?
Schedule 40 aluminum pipe is aluminum pipe manufactured or specified using an NPS and Schedule 40 dimensional system. The Schedule 40 wall thickness changes with the nominal pipe size.

What is the wall thickness of Schedule 40 aluminum pipe?
The wall thickness depends on the NPS. For example, NPS 1 Schedule 40 is about 0.133 in. thick, NPS 2 is 0.154 in., and NPS 4 is 0.237 in.

What is the OD of 1 inch Schedule 40 aluminum pipe?
The outside diameter of NPS 1 Schedule 40 pipe is 1.315 inches (33.4 mm).

What is the ID of 2 inch Schedule 40 aluminum pipe?
NPS 2 Schedule 40 pipe has an approximate inside diameter of 2.067 inches (52.5 mm) when using a 0.154 in. wall.

Is 6061-T6 available in Schedule 40 aluminum pipe?
Yes. 6061-T6 Schedule 40 aluminum pipe is commercially available in multiple NPS sizes. Products may be supplied as extruded or seamless pipe depending on the specification and supplier.

Is Schedule 40 aluminum pipe stronger than Schedule 80?
No. Schedule 80 has a thicker wall than Schedule 40 for the same NPS, but strength depends on the aluminum alloy, temper, dimensions, temperature, and design conditions.

Can Schedule 40 aluminum pipe be welded?
Yes. Aluminum pipe can be welded using suitable procedures and filler materials. However, welding can reduce the strength of heat-treated alloys such as 6061-T6 in the heat-affected zone.

What is the difference between aluminum pipe and aluminum tube?
Aluminum pipe is commonly specified by NPS and Schedule. Aluminum tube is normally specified by its actual outside diameter and wall thickness.

Is Schedule 40 aluminum pipe suitable for pressure applications?
It can be used in pressure applications when the material, dimensions, temperature, joints, and applicable design requirements have been properly evaluated. Schedule 40 alone is not a universal pressure rating.