If those calculators the previous posters suggested still don't work for you, you can use your boil kettle to mash in. Being able to direct-fire your mash tun allows you to easily hit your desired temperature. If you don't have a screen or false bottom in your kettle, just pour the whole mess into your cooler mash tun after 60' for lautering and sparging. I frequently do this when I step mash or do a hybrid step-decoction mash, and never had any problems.
The Fiesty(sic) Goat Brewery est. 2007 & Clusterfuggle Experimental Ales est. 2009
Planned: sLambic II, Flanders Red II
Primary: Saison, Berliner Weisse, Dark Mild, sLambic I
Secondary: Orange Blossom Mead, Flanders Red I
Kegged: Fat Man Porter w/ 1469, Fat Man Porter w/ 005, Centennial Falcon w/ Conan, Centennial Falcon w/ Denny's, Barrel-aged Fat Man Porter, Belgian Dark Strong
Bottled: Flanders Red I