Determining what size pipes you need for your project can be confusing. Many people assume pipe size is the outer diameter of the pipe—but “pipe size” actually refers to what is called “nominal diameter.”

Fittings can be just as confusing. Their inside diameters must be large enough to fit over the pipe’s outside diameter. A half-inch plastic elbow, for example, has an outside diameter of about 1-1/4 inches.

Use

this guide to help you find the pipe and fitting sizes you need for your next project.Convert Actual Diameter to Nominal Diameter The easiest way to find what nominal pipe size you need is to use follow these steps and use the conversion chart below. Pipe and tubing are not measured the same way. Tubing is measured and named based on the actual outside diameter of the tube.

PEX, or Cross-Linked Polyethylene Tubing, is another technology fast becoming popular, and it is measured and named by inside diameter.