Is my Efficiency calculation right?

[Dick562]

grain
6.5 pd us 2 row
1 pd maris outter malt

Batch size 2.5

pre boil 5 gallons

total points
111.4

Pre boil og
1.051

Mash Efficiency
45%

Dose this look right i dont have a post boil og if that matters (things fall)

 

[passedpawn]

You don't need to know the post-boil gravity to measure your conversion (mash) efficiency, but there is a very good reason almost everyone does (more on that in a minute *).

Assuming potential of 36 points for each grain, ideal conversion would give you

( (36*6.5) + (36*1) ) / 5g = 54 points (1.054). So, your efficiency is

measured / ideal =

51/54 * 0.94 = 94% Nice job [though I suspect bad measurement somewhere - weight, volume, or gravity]
​

* Thing is, if you measured your pre-boil gravity, it was probably hot and the reading would be way off (pardon me if you cooled it first).

This, BTW, is your conversion effiency; it just measures how well you extracted soluble sugars from the grain. Since losses can (and do) occur while transferring from the boil kettle to the carboy, that also will affect the final brewhouse efficiency. So, in the equation above, if you replaced the "5g" with the amount you transferred to the carboy, and you replace the gravity (1.051) with the gravity of the final cooled wort, then you would get your total brewhouse efficiency. It won't get better, and will likely get worse

 

[Dick562]

Thank you, i will write that down and see what i get for my next batch if i dont brake my hydrometer a second time. Yea i didnt get a 94% for brewhouse efficiency i can tell you that lol but thank you for the good news on the conversion at least i will get some info out of this batch.

 

[passedpawn]

Thank you, i will write that down and see what i get for my next batch if i dont brake my hydrometer a second time. Yea i didnt get a 94% for brewhouse efficiency i can tell you that lol but thank you for the good news on the conversion at least i will get some info out of this batch.

FYI, most hydrometers are calibrated for 60 degree wort. Off by a few degrees doesn't make a diff, off by 10 degrees and it's off by 1 or 2 points.. but if you measure wort at 150 and it is way way off. There are correction tables, and software will correct this as well, but if you want to measure pre-boil it's best to cool sample before reading the SG, or use a refractometer.

 

[Dick562]

it was at 74 so plus one makes it 1.051 thats what the paper says i just hope i hit my post boil OG of 1.070 not likely but i can live with it for my first batch.