Like many brewers, I use recipe software (BeerTools Pro in my case) to design recipes, log notes, track inventory, etc. And I really like it; the only thing it won’t do is estimate my efficiency based on the actual mash parameters. Hence this little tool, which does exactly that (and pretty much only that). For documentation, please see Batch Sparging Theory.
If you have any feedback on the calculator, feel free to contact me.