First Post...and Yeast Effeciency Question

Hi All:

First post to a great forum! I've been lurking for a month now.

I have a question about the "yeast efficiency" concept.

I have only brewed two batches so far (BTW, this is very fun) and here are my numbers:

1st Beer (all extract) - 1.052 OG @70F, 2nd reading of 1.020@70F. Calculation is as follows:
(1.052 - 1.020) x 105 = .032 x 105 = alcohol by weight (3.36%). To convert to volume multiply the result (.032) by 1.25 = 4.2% by volume.

Is this first beer's efficiency?: (1.020 / 1.052) * 100 = 96.95%

AND

2nd Beer (partial mash) - 1.053 OG @130F. Add .013 for temp adjustment = 1.066 OG . 2nd reading of 1.020 @70F.
(1.066 - 1.020) x 105 = 4.83% by weight
4.83 x 1.25 = 6.038 by volume
Is this second beer's efficiency?: (1.020 / 1.066) * 100 = 95.68%

Are my numbers on target here?

If I'm calculating yeast efficiency correctly, are these numbers good?

Thanks,
Spindrift

Edited for a typo.

Dude,
If this is batch #2, I would worry more about how it tastes....
I do admire your mathematical approach, though.

Jpuf

Yeast attenuation: (part of the fun is learning the lingo)

Take the points of the OG - points of FG and divide by points of OG

(52-20)/52 = 61% not bad not good. 70-75% is typical for most yeasts.

The calculation you really need to make is Target Gravity or what should my FG be?

Points of OG * (1- yeast attenuation) = TG

52 *(1-.75) = 13 or 1.013