If you are working on a plumbing, construction, or other type of project, you need to know what the size of a galvanized pipe is.
One of the most common questions we receive from customers at BobCo Metals is, “What is the outside diameter of a 3/4 inch galvanized steel pipe?”
It sounds simple enough, but pipe sizing can be a confusing thing if you don’t understand how it has been (and still is) measured.
Nominal vs. Actual Pipe Size
Pipe measurements in the U.S. are typically given using Nominal Pipe Size (NPS). This refers to the approximate inside diameter (ID) of the pipe, not the actual outer dimension. The outside diameter (OD) of a pipe is usually larger than its nominal size.
This is why a 3/4 inch galvanized pipe doesn’t measure 0.75 inches on the outside. Let’s look at the actual measurements.
Actual Dimensions of 3/4 Inch Galvanized Pipe
| Nominal Pipe Size | Inside Diameter (Approx.) | Outside Diameter (Actual) |
| 3/4 inch | 0.824 inches | 1.050 inches |
So, if you’re buying or cutting 3/4 inch galvanized pipe, you’ll be working with an actual outside diameter of 1.050 inches.
What About 3-Inch Galvanized Pipes?
If you're working with larger sizes like the 3-inch galvanized pipe or 3-inch galvanized steel pipe, the same sizing rule applies. The nominal size refers to the inside diameter, not the outer one. For a 3-inch nominal pipe, the actual inside diameter is approximately 3.068 inches, while the outside diameter is 3.500 inches. That means a 3-inch galvanized steel pipe will measure 3.500 inches across the outside, not 3 inches as the name might suggest. This is important to keep in mind when planning for fittings or clearance in your project.
Why Pipe Sizing Matters
The fit that’s right makes a difference with everything from plumbing connections and welding to structural support and railing systems. Getting the outside diameter right is a central concern, since this determines the fit of a hose or system component, as well as the material's need to withstand crimping, cutting, or other compressive forces.
Need Galvanized Pipe in Los Angeles?
BobCo Metals in Los Angeles has been providing clients with a variety of steel products for sale, including steel tubing and piping. Whether you need a 3-inch galvanized steel pipe, a 3/4 inch fixture, or a 1-1/2 inch cover plate, we have the materials you need at highly competitive prices.
Check out BobCo Metals for the appropriate dimensions of a galvanized pipe and no-nonsense advice and assistance on your next project!
