I'm not sure if there's a thread for this already. Just wondering if there was a collection of formulas and calculators for formulas anywhere e.g. mash/ stike temp calculator or efficiency formula.
Yup. All compiled into one tidy, easy to use interface, and it's FREE and open source (you can see how the calculations are done--and even change them if you want, when you want).
This spreadsheet. You'll need OpenOffice (also FREE and open source). The sheets are protected (without a password) simply to prevent overwriting the formulas. You can unprotect them easily should you want to change something.