What is the outdoors diameter of Schedule 40 galvanized pipe?

The outside size of Schedule 40 galvanized pipe can differ depending upon the small size of the pipe.

Below are the generally approved nominal dimensions and their equivalent outside sizes for Schedule 40 galvanized pipe:

For 1/8-inch small dimension (NPS 1/8):.

Outside Size: 0.405 inches.
For 1/4-inch nominal size (NPS 1/4):.

Outside Diameter: 0.540 inches.
For 3/8-inch small dimension (NPS 3/8):.

Outside Diameter: 0.675 inches.
For 1/2-inch small size (NPS 1/2):.

Outdoors Size: 0.840 inches.
For 3/4-inch small size (NPS 3/4):.

Outside Size: 1.050 inches.
For 1-inch small size (NPS 1):.

Outside Size: 1.315 inches.
For 1 1/4- inch nominal dimension (NPS 1 1/4):.

Outdoors Diameter: 1.660 inches.
For 1 1/2- inch small size (NPS 1 1/2):.

Outside Diameter: 1.900 inches.
For 2-inch small size (NPS 2):.

Outdoors Size: 2.375 inches.
For 2 1/2- inch nominal size (NPS 2 1/2):.

Outside Size: 2.875 inches.
For 3-inch small dimension (NPS 3):.

Outside Diameter: 3.500 inches.
For 4-inch nominal size (NPS 4):.

Outdoors Diameter: 4.500 inches.
These are standard dimensions for Schedule 40 galvanized pipe according to ASTM specs. It is very important to keep in mind that these measurements are small sizes and may differ slightly due to making resistances. For exact dimensions, it’s advised to get in touch with the producer’s specs or use calipers to gauge the real outside diameter of the pipeline.