Not sure if Siri or you are aware, but Attackpoint has a feature which will calculate your training paces. At the bottom of screen is an item, "paces".
It calculates your Vdot (which is the orange number it adds to your log when you note that it was a "race"). It then will give you paces for the various workout types. It also will calculate equivalent race times based on that Vdot.
Really an excellent tool, thanks to Kenny.(and Jack Daniels)