Maybe I just don't know where to look, but there doesn't seem to be a single source for standard homebrewing calculations. Sure I find them on the Internet and in books on brewing, but many of them are different and yield close, but not exact results. Is there an AHA or BJCP "sanctioned" or "recognized" set of brewing calculations out there for the homebrewer to use?

I ask because I would like to develop my own spreadsheet application for recipe design and result estimations. I know there's a ton of software already written, but even the commercial software packages results seem to vary.