Natural gas pipe sizes vary depending on pipe material, gas pressure and pipe length. Typical nominal pipe diameters in steel are tabulated in the Schedule 40 table, where the smallest nominal pipe diameter is half an inch and the largest diameter is 8 inches.
The Type K table lists the diameters of copper tubing for natural gas, with the smallest nominal pipe diameter for this material being ? inch and the largest being 1 ? inches. Another series of copper tubing, Type L, is made of a stronger grade of copper and is thus thinner, although the nominal diameters in this size are identical to Type K.
Low pressure natural gas pipeline capacity can be calculated using the empirical Spitzglass formula, which accounts for the natural gas flow capacity (cfh), the pressure drop in water column, the pipe length in feet, an empirical factor (k) calculated from the inner diameter of the pipe and the specific gravity of natural gas, normally set to 0.60. High pressure gas lines are subject to an extended form of the Schedule 40 table for steel pipes, which accounts for downstream and upstream pipe pressure, gas compressibility and a fittings safety factor that depends on pipe length.