brewhouse efficiency question

Hi. i need help on determining my actual efficiency. I estimated my efficiency at a higher number when building by recipe and have re-adjusted them since but now I’m confused.
here are all my numbers
my mash thickness ratio was about 1.3qt/lb, mashed for 60min about 155F

original estimated OG (at 70%) was 1.082 and my actual OG was 1.070. according to my efficiency calculations i should have been at 1.060 (50.4%)

had i had 15.5lbs of grain and sugar, 5gal of wort collected, my preboil og was 1.0568

here was my equation= (18.925L)(1.070gravity)(.175plato as a decimal)= 3.5437  then i divided by my total weight was 3.5437/7.03068= .5040 or 50.4%.
my question how is how is actual og higher than the adjusted og? Shouldn’t my efficiency be closer 64%?
i do batch sparge, if that makes any difference.

Me and math are not friends so i could be missing something, so any suggestion or edits are welcome
thanks

I would spend a couple of $ and get some brewing software.  I can’t do the math either…

Dave

If you don’t want to spend money on software, there are two freeware programs you could check out.

Web Page Under Construction - QBrew
http://www.brewtarget.org/ - BrewTarget

I don’t have the link, but if you hunt around I’m sure there are on-line calculators as well.

On average most base malts will give you about 36ppg (points per pound per gallon). Specialty grains vary but tend to be somwhere between 25 and 30ppg. So if you have 15.5lbs of grain the calculation would be 15.536=558 then divide by batch volume (5 gallons). 558/5= 111.6. Then multiply by your expected efficiency. 111.6.70 = 78.12 so your OG should be about 1.078 at 70% efficiency.

To figure out your efficiency for a particular batch you can take your gravity 1.070 and drop the “1.0” so you have just the 70 part. Divide by the result of your total gravity points/volume. (558/5=111.6). So 70/111.6 =0.63 …so 63% efficiency.

Your mash efficiency would actually be lower than that 63% because of the sugar contributing 100% extract by mass.

thanks for the help

That’s true, I must have overlooked the sugar part.

I use this one: http://powersbrewery.com/beer-recipe-calculator/