Noimus

One stage raises it 50%. For instance, a Pokemon with a stat of 350 raises it to 525 at +1.

I moved your question about Speed boosts to this thread, where it belongs: http://www.smogon.com/forums/showthread.php?t=70306&page=139. Incidentally, when you increase Speed two stages, it doubles. So a +2 Adamant Lucario reaches 558 speed.