Can somebody check my math? (calculating skirt length)

[gem]

Ok, so I had Milord measure me for skirt length for my Italian overgown tonight.  He measured from the raw edge of the bottom of the bodice.  The length from that to desired finished length is 38.75".

Add 2" for hem allowance:  40.75"

Plus 1/2" for seam allowance at the waistline: 41.25".

Now here's where I'm not sure:  The bodice/waistline has a half inch seam allowance.  Since Milord measured from the raw edge, does that mean I need to *subtract* half an inch from the total skirt length I just calculated? 

(Gem's dyscalculia rears its ugly head...)

Thanks!

[I. Stewart]

Make it about six inches longer than you need it to be, then hem to length.  If you try to measure exactly, something will go wrong and it will be too short.  At least that's what happens to me..  Anyway that's my advice.  Give yourself plenty, then finish.

[sealion]

It's early and I haven't had my coffee so I might not be thinking straight LOL but I would add a half inch because if he had measured from the seam line instead of the raw edge the measurement would have been taken a half inche higher, not lower. But, yeah, do as I Stewart says and give yourself a little more leeway if you have enough fabric to do so.

[LadyShadow]

I agree with Sealion.  Since it was measured from raw edge I think you would add.  But totally agree with I Stewart.  I always add extra on the length of the skirt and then trim and hem to the desired length.  I usually tend to mess up dramatically if I do the just exact measure.

[gem]

Make it about six inches longer than you need it to be, then hem to length.  If you try to measure exactly, something will go wrong and it will be too short.  At least that's what happens to me..  Anyway that's my advice.  Give yourself plenty, then finish.

Oh, gawd.  THIS is exactly why I have you people.    I forgot I was pleating this, and that that will eat up length in crazy, unpredictable ways.

(thank you)