Well i have some custom exhaust that I dont know what the heck it is, the pipe to the muffler measure 9.5" in diameter (tape measure wrapped on outside of pipe)....Which makes me think it is a 3.5" exhaust system? But i am not sure and thats why Im posting here, any help is appreciated

 

first off, the diameter is the distance across the tube, not around like you measured it.

here you go: http://mathworld.wolfram.com/Diameter.html

when referring to tubing sizes, one usually would use the diameter measurement, so measure what the diameter of the pipe is, and thats your size.

 

3" Tube has circumference of 9.4245, 3 1/5" is 10.99"

 

excellant, thanks a lot, and ya i meant circumference not diameter, my bad

 

pi times radius squared is the correct equation so 9.5 divided by pi is 3.023943919

then find the square root to get 1.738949085

then double to find the diameter of 3.477898169

so 3.5" sounds about right

 

huh??? 3" tube diamter is 7.068583471 and 3.5" is 9.621127502 remember it's pi times radius squared.

 

pi times radius squared is to get the area of a circle,
circumference is diameter times pi

"When the distance from the center to the outside of a circle is its radius (half its width), and its width is its diameter, the circumference (or perimeter) of a circle equals two times radius times pi (3.14159), or diameter times pi. The area of a circle equals pi times radius squared"

http://www.artlex.com/ArtLex/c/circle.html

 

Iroc's got it, its 3" thanks again guy, thats a nice math site too

 

Tubing is measured on the outside diameter and pipe is measured on the inside diameter up to 12".