I just purchased OnTarget Precision Calculator v2.25 last night for $11.99 (the free version v1.10 is no longer available). You get a 15 day trial and it works pretty slick. It's a bargain at $12. I love shooting, but I hate measuring targets.

“There are three things all wise men fear: the sea in storm, a night with no moon, and the anger of a gentle man.”
― Patrick Rothfuss, The Wise Man's Fear