Efficiency; equation help please

[J-stone]

So, after my first AG batch I would like to know what my efficiency was. I tried running the numbers myself and I must be wrong.

2-Row Malt 9lbs
carafoam 0.5lb
OG about 1.058

I came up with 80%, is that right?

 

[batty]

One critical piece of information missing here.. how much (volume) did you end with??

Could also do a quick double-check w/ this website: http://www.brewersfriend.com/brewhouse-efficiency/

 

[J-stone]

Wow, I guess that afternoon homebrew hit me hard yesterday. . . 4.5 gal end volume. . . Sorry about partial info

 

[batty]

No worries. When I do the calc I get 74.7% efficiency - (58x4.5)/(9x37+0.5x33)

Matches pretty well with the online calc I noted above (74.25%).. depends a bit on what source you look at for each grains ppg.. varies a bit.