How to determine FG?

[brockchance]

I've done a couple brews now, but when I first started I ordered a kit with grain and a mr beer refill. I figured I'd do the mr beer to get the feel of fermentation and bottling but the other kit beat it in the mail and I couldn't resist. So the mr beer was forgotten about until the other day..... It was a Northwest Pale Ale says mr beer I changed yeast (us-05) and dry hopped (Cluster leafs) because I like to do things my way😎 Well since mr beer is pretty basic I really don't know what my FG should be. For this batch and future ones how do I figure what my final should be??

 

[unviewtiful]

All kits that I've seen have an estimated FG in the instructions. If it doesn't, you could try plugging it into a free brewing software (such as brewers friend) and see what it says.

But really, what it "should be" is irrelevant once you pitch yeast. It's done fermenting once you get the same reading a couple days apart. If you package once you hit a particular number and it's not stable, you run the risk of bottle bombs.

 

[m1k3]

Short answer is you cannot calculate a FG.

Long answer: The apparent degree of fermentation (ADF) for US-05 is 81% for a "standard wort". But no real world wort is standard. so you can expect the OG to drop about 81% but that is not going to be exact.

Most people will just wait for fermenation to look finished and then give a few days at temperature (or warmer) just to make sure.

The other suggest practice is to take 2-3 gravity samples (2-3 days apart) to ensure the FG is stable.