Exhaust measurement

[Spyda]

I have a full exhaust siting in my garage (Thanks GOLFBALLS) and i want to know how to measure the diameter of the pipe.

Do i measure from the outer edge to outer edge or inner edge to inner edge?

[GoLfMan]

do the outside, the wall lining shouldnt be that thick as to make a huge difference in the reading.

Just round it up or down to the nearest inch.

use a Vernier or a micrometer.... good luck!