Stainless steel tubing is typically sized using its outside diameter (OD) and wall thickness, which together determine the inside diameter (ID). Understanding how these measurements relate, and how tubing sizing differs from pipe sizing, can make it easier to identify the right dimensions for a specific application.
Understanding Stainless Steel Tubing Sizes
Choosing the right stainless steel tubing involves more than finding a diameter that looks right for the application. Outside diameter, inside diameter, and wall thickness all affect how tubing fits with other components and whether it meets the requirements of the job.
A misunderstanding of those dimensions can lead to compatibility issues, rework, or delays when tubing doesn’t match the equipment or connections it was intended for.
Knowing what each measurement represents and how the dimensions relate to one another makes it easier to read tubing specifications and determine what an application actually requires.
OD vs. ID vs. Wall Thickness
Outside diameter, inside diameter, and wall thickness describe different parts of stainless steel tubing, but the three measurements are directly related. Understanding what each one represents makes it easier to read tubing specifications and compare sizes.
What Is Outside Diameter (OD)?
Outside diameter, or OD, is the measurement across the tube from one outside edge to the other. Because stainless steel tubing is commonly specified by its OD, this measurement is especially important when the tubing needs to fit with equipment, connections, or other components.
What Is Inside Diameter (ID)?
Inside diameter, or ID, measures the open space across the interior of the tube. ID can affect factors such as the amount of space available for fluid or other material to pass through the tubing.
Unlike OD, the inside diameter changes with wall thickness. Two tubes can have the same OD but different IDs if their wall thicknesses are different.
What Is Wall Thickness (WT)?
Wall thickness measures the distance between the outside and inside surfaces of the tube. For a given OD, increasing the wall thickness reduces the available inside diameter.
If you know the OD and wall thickness, you can calculate ID using:
ID = OD − (2 × Wall Thickness)
Wall thickness may also be identified by gauge. American Stainless supplies tubing in several wall thicknesses, including:
- .020″ — 25 gauge
- .035″ — 20 gauge
- .049″ — 18 gauge
- .065″ — 16 gauge
- .083″ — 14 gauge
- .120″ — 11 gauge
Within this gauge system, a lower gauge number corresponds to a thicker tube wall.
Stainless Steel Tubing Size Chart
Stainless steel tubing is available in a range of outside diameters and wall thicknesses to meet different application requirements. American Stainless supplies tubing from 1/8″ IPS through 12″ OD, with multiple wall thicknesses available.
The chart below shows the wall thicknesses and corresponding gauges available through American Stainless:
| Gauge | Wall Thickness |
|---|---|
| 25 gauge | .020″ |
| 20 gauge | .035″ |
| 18 gauge | .049″ |
| 16 gauge | .065″ |
| 14 gauge | .083″ |
| 11 gauge | .120″ |
For any given OD and wall thickness, the inside diameter can be calculated using:
ID = OD − (2 × Wall Thickness)
For example, a 1″ OD tube with a .065″ wall thickness has an ID of .870″.
Available combinations can vary by tubing size and specification, so the gauge and wall thickness options above shouldn’t be interpreted as available across every OD.
Stainless Steel Tubing vs. Pipe Sizing
Stainless steel tubing and pipe are not sized the same way. Tubing is generally specified using its actual outside diameter and wall thickness, while pipe is commonly identified by a nominal pipe size (NPS) and schedule.
With tubing, a 1-inch OD means the outside diameter actually measures 1 inch. The wall thickness then determines the inside diameter.
Pipe sizing works differently. A nominal pipe size is a standardized designation and does not necessarily correspond to the pipe’s actual OD or ID. The pipe schedule identifies the wall thickness, which also affects its inside diameter.
The distinction is important when reviewing specifications or ordering material. A 1-inch tube and 1-inch nominal pipe are not interchangeable simply because they share the same stated size.
How to Choose the Right Stainless Steel Tubing Size
Choosing the right tubing size starts with understanding what the tubing needs to do and how it needs to fit within the application. A single measurement isn’t enough to make that determination.
Consider:
- Outside diameter: What equipment, fittings, or other components does the tubing need to fit or connect with?
- Inside diameter: How much internal space is required for the application?
- Wall thickness: What strength, pressure, and operating conditions does the tubing need to accommodate?
- Material grade: Which stainless steel grade is specified for the operating environment?
- Application requirements: Are there engineering specifications or other requirements that dictate the tubing dimensions?
These factors work together. Two tubes with the same outside diameter can perform very differently when their wall thickness, inside diameter, or material specifications change.
Before ordering, confirm the complete tubing specification rather than relying on diameter alone. This can help avoid fit issues, incorrect material, and unnecessary delays once the tubing reaches the job.
Stainless Steel Tubing Sizes FAQ
How is stainless steel tubing measured?
Stainless steel tubing is generally specified by its outside diameter (OD) and wall thickness. These measurements can also be used to calculate the tubing’s inside diameter (ID).
Is stainless steel tubing measured by ID or OD?
Stainless steel tubing is typically specified by its outside diameter and wall thickness rather than its inside diameter alone. The ID will vary depending on the thickness of the tube wall.
What is the difference between pipe and tubing sizes?
Tubing is generally sized using its actual outside diameter and wall thickness. Pipe typically uses nominal pipe size (NPS) and schedule, so the stated pipe size does not necessarily represent its actual OD or ID.
How do you calculate the ID of stainless steel tubing?
Subtract twice the wall thickness from the outside diameter:
ID = OD − (2 × Wall Thickness)
For example, tubing with a 1″ OD and .065″ wall thickness has an ID of .870″.
What wall thickness do I need?
The appropriate wall thickness depends on the requirements of the application, including pressure, strength, operating conditions, and applicable engineering specifications. Wall thickness should be evaluated along with OD, ID, and material grade rather than selected on its own.
What stainless steel tubing sizes are available?
American Stainless supplies stainless steel tubing ranging from 1/8″ IPS through 12″ OD, with multiple wall thicknesses available. Availability varies by size and specification.
How do I choose the correct stainless steel tubing size?
Start with the dimensional and performance requirements of the application, including the required OD, ID, and wall thickness. Also account for the components the tubing must connect with, the specified stainless steel grade, and any applicable engineering requirements.
Getting Stainless Steel Tubing Sizing Right
Stainless steel tubing sizing comes down to understanding how outside diameter, inside diameter, and wall thickness work together. Getting those dimensions right makes it easier to match tubing to the connections, equipment, and performance requirements of the application.
American Stainless & Supply stocks stainless steel tubing from 1/8″ IPS through 12″ OD, with multiple wall thicknesses available. Whether you know the exact dimensions you need or are working from an established specification, our team can help you find the tubing that matches your requirements.
Explore our stainless steel tubing options, review pipe sizing for alloy & plastics, or contact our team to discuss your next order.