What are the dimensions of ANSI flanges?

Manufacturers do not make flanges in one standard dimension. Manufacturers produce American National Standards Institute certified flanges with nominal pipe sizes ranging from 1/4 inch to 24 inches and diameters ranging from 3 3/8 inches to 46 inches.

Plumbers use flanges to support joints or connections between pipes. The American National Standards Institute provides pressure class and bolt standards for different sized flanges to ensure safety. The Engineering Toolbox provides a comprehensive listing of nominal pipe sizes, dimensions and classes of ANSI certified flanges. The website also lists specifications about the number and size of bolts to use with the different ANSI flanges.