Frank99

Recipes 

I just did my 1st all-grain batch and have a question:
I have a gravity reading from right after the sparge of say 1.04.
I then boiled the 8 gallons of wort down to 5 gallons.
Unfortunately, I don't have a gravity reading after the boil as my hydrometer broke. How can I figure out the post boil gravity?

VictorWI

Recipes 

The calculations I've seen for evaporation are:

FinalGravity = (InitGravity - 1) * 1000 * InitialVolume / FinalVolume / 1000 + 1

So in your case

(1.040 - 1) * 1000 * 8 / 5 / 1000 + 1

Which is 1.064.

Frank99

Recipes 

Thanks! Surprisingly that puts me right where I should be.