I have "Winmiter" and "Tubemiter". Both these are freeware.
Pipe diameters can be entered into "Tubemiter" only by metric (mm) values.
"Winmiter" allows for input in either mm or inches.
However, "Tubemiter" uniquely allows for the WALL THICKNESS of the pipe. If "Winmiter" allows for this I'm not aware of it.
Yesterday I used "Tubemiter" for the first time to cut parts for an anvil stand out of 2 1/2" pipe.
I printed out a template, cut it out with scissors, and wrapped it around the pipe. I used a center punch to scribe the line in the rust on the pipe. Put it in the chop saw mitered to 45 degrees. Cut to the line. Changed the miter fence to a square cut. Cut of the "points" of the cut by just "eyeballing" it.
To my surprise, each of the three fish mouths was darned close to a perfect fit. To my even greater surprise, all of the tripod legs were of the same length. Of course, if I'd attempted to build a FOUR legged stand, NONE of 'em would have been even close.
The interesting thing about "Tubemiter" is that it uses the additional parameter (wall thickness) to generate TWO curved lines. The difference between these reminds me of the "wing tip" on "wing tip" shoes. Apparently it represents the material that has to be removed to get the joint to fit up.
In other words, if you were to taper the INSIDE of the pipe wall to fit the joint, the outer wall would represent the outer line in the template, and the inner wall would match the shape of the inner line.
I've had very little experience with either of these programs. But I think I like "Tubemiter" a tad better.