What is the inside diameter of copper pipe?
In the plumbing trade the size of copper tubing is measured by its outside diameter in millimetres. Common sizes are 15 mm and 22 mm. Other sizes include 18 mm, 28 mm, 35 mm, 42 mm, 54 mm, 66.7 mm, 76.1 mm, and 108 mm outside diameters. Type M half-inch pipe has a wall thickness of 0.028 inches while type L is 0.040 inches.