I ask because I know what the standard pipes available are, and there are a few formulas out there. For my project the numbers come up shorter than what is available over the counter. Even with the mid-range enhancing length. Just wanted to check the numbers. For what it is worth I like this calculator: http://www.mez.co.uk/mezporting/exhaust_length.html
Pete...I'm gonna save that post. I've been wanting to write a piece of exhaust software to go along with my Helmholtz resonance software for calculating intake track length.
Tuning for Speed has some similar info.
You know what I've done in the past. Find a good picture of a factory race bike of similar displacement and cylinders to yours....import it into a CAD program....scale it using the rim size....measure the primary pipe length, megaphone length and taper.
I've even used calipers on the parts of high quality models of old Honda GP bikes....you'd be amazed how accurate they are.