Efficiency Check...

Hello all. I'm relatively new to all grain brewing and have not quite mastered the efficiency calculations yet. I did find some calculators and such for this but I wanted to do it by hand as well. Here is what I did (please correct me if I'm wrong):

Recipe:
12 lbs Maris Otter Pale
0.5 lbs Brown Malt
0.5 lbs Special B Malt
0.5 lbs Chocolate Malt

I came out with a pre-boil gravity reading of 1.063 with 5.8 gallons.

I used Course Grind Dry Basis (CGDB) values for all the grains since the grains were only run through the grain mill once and the mill was somewhat old producing a courser grind...

Calculations:
-Maris Otter:
80.73% x 46ppg x 12.0 lbs = 446 gravity points

-Brown Malt:
75.07% x 46ppg x 0.5 lbs = 17.2 gravity points

-Special B Malt:
63.7% x 46ppg x 0.5 lbs = 14.6 gravity points

-Chocolate Malt:
61.26% x 46ppg x 0.5 lbs = 14.1 gravity points

TOTAL = 491.9 gravity points

1.063 means 63 points/gallon x 5.8 gallons = 365.4 points

Therefore 365.4/491.9 gives me an efficiency of 74.3%?

ALSO... I didn't have a hydrometer when I was brewing so I wasnt able to take a sample of my post-boil OG... I saved a sample of the pre-boil which is how I got the value above. To get an estimate of my post boil OG, is this the correct calculation?

365.4 points/4.75 gallons = 76.9 points/gallon or a reading of 1.063?

Thanks for taking a look!

No expert here, but the calculation I found is

CGDB - MC (Moisture Content) -.002 * 46.214

So for example

(.8073 - .04 - .002) * 46.214 ppg x 12.0 lbs = 424 gravity points (rounding), so that is a difference of 22 from your calc.

Now I have no idea which is right, but I would think CGDB - MC * 46ppg would be a good estimate and what I'm going to be using. The only thing I see wrong is not taking into account the MC. Again I'm no expert, but whoever wrote the article below seems like they might be.

BMG - Understanding Malt Analysis Sheets -- How to Become Fluent in Malt Analysis Interpretation

I would say you calculated pretty well. Promash has it at 73% preboil and I did not know the specifics of your grain bill as far as potential parts per pound. It should be close though.

Try this ..... final gallons x gravity / pounds of grain / 37 = eff%
Elample:10 gal final boil
gravity 1.054
15.75 lbs of grain
10 x 54 / 15.75 / 37 = 92

Thanks everyone!

This is how BeerSmith thinks your gravity units are totaled which is pretty darn close to what you have above:

12 lb Marris Otter = 12(38) = 456 GU
0.5 lb Brown = 0.5(32) = 16 GU
0.5 lb Special B = 0.5(30) = 15 GU
0.5 lb Chocolate = 0.5(28) = 14 GU

13.5 lb Total Recipe = 501 GU

so 5.8 gallons of 1.063 means your preboil runnings had 5.8(63) = 365.4 GU
for a mash/lauter efficiency of 365.4 GU / 501 GU = 72.9%