Brewed a 3 gallon biab batch this past weekend. After the 60 min boil I ended up with 2.75 gallons in the fermentor, including trub, so about 2.5 gallons of liquid. Post boil gravity was 1.050, looking for 1.044.So I topped up with purified water(about 1/2 gal) to 3.25 gal in the fermentor, figuring I had roughly 3 gal of liquid now.
My question is in trying to estimate OG. Didn’t want to take another sample since it’s a small batch. Here’s my math, please correct me if I’m off:
.5 gal @ 0 SG
2.5 gal @ >050 SG
Total 3.0 gal/.5 = 6
50 x 5 + 1 x 0 = 250/6 = 41.667 so, OG of +/- 1.042
I’m sure even if this is correct, there is an easier formula.
Thanks for any schooling. If nothing else, I’ve learned that I’m boiling off more than my system had allowed for, so adjusting shouldn’t be too hard.