Size matters, especially when you’re purchasing tubing for your upcoming projects. And when deadlines are looming and budgets are tight, there’s no room for error. Ending up with the wrong size tubing for your project means compatibility and potential safety issues, expensive rework, and bloated project lead times—and all of those contribute to poor project results and massive headaches all around.
The best way to keep any project on track is to pay close attention to your project specs early in procurement. But it isn’t always easy to understand the sizing specifications for steel tubing. Minimize your risks of sizing errors and keep your projects running smoothly—without blowing past your deadlines or your budget ceilings—with tips on how to navigate stainless steel tubing specifications from our PVF procurement experts.
How to Read a Stainless Steel Tube Sizing Guide
To know how to purchase the right size steel tube and ensure your procurement decisions are spot-on and hassle-free, you first need to know how tubing sizes are measured. Every length of steel tubing has three size-related specifications you need to pay attention to. These measurements are:
1. The Outside Diameter (OD)
The outside diameter of your tubing refers to the distance across the outside of your tube. Look at your tubing head-on and imagine it’s a flat ring instead of a three-dimensional space. If you mark a point on one outer edge of your tube’s cross-section, mark another point on the opposite side, and measure the distance between the two points in inches, you’ll find its OD.
Put simply, the OD is a measurement of how wide the outside of your steel tubing is.
2. The Inside Diameter (ID)
Likewise, you also have the inner diameter of your tubing to pay attention to. This measurement works the same in practice as the OD, except instead of drawing and connecting points on the outside of the ring, you’re drawing your points on the inside and measuring the distance between them.
Put simply, the ID is a measurement of how wide the inside of your steel tubing is.
Instead of ID, steel tubing suppliers might instead use IPS in their stainless steel tubing specifications. IPS stands for Iron Pipe Size, a sizing system based on a pipe’s inside diameter developed in the early 19th century. Today, IPS is still used by some major manufacturers, particularly PVC pipe and tube.
When looking for a range of tube sizes offered by a tubing manufacturer or distributor, you’ll typically see a range from the smallest ID/IPS to the largest OD. For example, at American Stainless, we stock steel tubing with IDs as small as 1/8” IPS and OD as large as 12”. The size range we offer is 1/8″ IPS – 12″ OD.
3. Wall Thickness (WT)
You know the outside diameter of your tube. You know its inside diameter or IPS. What other number helps you know how to select tube sizes for your projects? You need the number for the space between the OD and the ID—and that space is the thickness of the tubing’s walls.
While technology has come a long way to make stainless steel tubing smaller and thinner, it’s not physically possible for your OD and ID or IPS to be the same. WT measures the distance in inches between the inside and outside diameters.
You can figure out the thickness of a pipe’s walls on your own just by subtracting the ID from the OD, but usually, your supplier will save you the trouble and provide the WT metric on its own.
WT is often provided in inches, but when you’re shopping around for steel tubing, you might also see the side listed in gauge. Understanding the gauge of a piece of tubing at a glance can be more difficult than WT. WT is provided in inches, and the bigger the number, the thicker the wall. However, gauge size is inversely related to wall thickness—so a larger tube wall thickness means a smaller gauge.
Here’s an example, using the stock stainless steel tubing specifications here at American Stainless:
- .020″ (25 gauge)
- .035″ (20 gauge)
- .049″ (18 gauge)
- .065″ (16 gauge)
- .083″ (14 gauge)
- .120″ (11 gauge)
As you can see, as the WT goes up, the gauge goes down. In most parts of the world, tubing gauge is standardized according to the Birmingham Wire Gauge (BWG) system. There are other wire gauge standards that can be used, but if you see a gauge listed without a specific reference system included, you can usually safely assume it is BWG.
So, put the numbers all together, and what do you get?
- You know how big your tubing is on the outside.
- You know how big your tubing is on the inside.
- You know how thick your tubing’s walls are.
With the knowledge of how these stainless steel tubing specifications work, you can confidently procure materials that fit your projects to a tee.
American Stainless: Your Source for Stock and Customizable Stainless Steel Tubing
Across the US Southeast, construction contractors and pipe fabricators in steel and paper mills, pharmaceutical and chemical plants, food and beverage processing facilities, and more turn to American Stainless for reliable, quick-turnaround steel tubing supply.
Our relationships with over one hundred leading PVF manufacturers means you can trust us to provide a wide range of high-quality, durable, reliable stainless steel tubing to match your project’s specifications. If what you need can’t be found off-the-shelf, we can leverage our manufacturer connections to fabricate custom tubing that meets your specs.
If you’re curious about the full range of sizes and gauges we have to offer, reach out to us to receive a complete stainless steel tube sizing guide. You can also start a quote to learn more about our stock and custom tubing options: