Darn. I just found this here on the big black header bar that Bob McC. has on home page… That is something I been looking for for a long time other than fig. out things on a scale ruler and lots of pencil work…
http://www.largescalecentral.com/pages/scalecalc
Really works great from what we use on scaling from Ho to Garden R.R. and back again. Tks Bob.