Audacity 2.1.0 Concert pitch

I’ve made some recordings that I’d like to keep - guitar and vocals - but my guitar was not tuned to 440. I’m having great difficulty trying to correct it in Effect/Change Pitch. I hear it slightly out when I raise or lower the pitch. Is there a way I can correct it to 440? cos no matter how I try, my ears can’t quite pin-point this exactly.
Audacity 2.1.0
Windows 7
Service Pack 1

Select a section of one of the recordings with a clear sustained note and go to Analyze → Plot Spectrum. Set it to Algorithm: Spectrum, Function: Hanning, Axis: Log, and Size as high up as you can go before it says there’s not enough data ought to be good. Expand this window out horizontally so you can see it better and then place your cursor at the lowest frequency peak so that the vertical gray bar following your cursor snaps onto it and the frequency + note on the right side will be the value for that peak. As far as I know there’s no way to get it to show you how many cents it’s off but you can enter the frequency in Hz to’s Hertz Calculations: Conversion page and it’ll tell you the note and cents away from the note in 440 tuning.

If you can’t “zoom-in” on the correct pith-change with trial-and-error, maybe the guitar wasn’t in-tune with itself? Are the vocals in-tune with the guitar? Are the vocals & guitar mixed together on the same track?

You might try [u]GSnap[/u] which is a free AutoTune like plug-in. (I’ve never used GSnap but I assume it won’t work if the vocal & guitar are mixed.)