Correct ABV estimation?

[jack13]

I'm going to be giving out bottles of a beer to strangers, so I want to get the ABV right, or at least not be significantly off. So I'd like to know if I'm doing this correctly:

Just finished primary fermentation with a 1.067 OG beer. FG was 1.014, so it's 7% ABV now.

Racked into secondary onto 2lbs honey. About 4.75 gallons in there.

I've read differing accounts, but one was that 1lb of honey in 5 gallons increases gravity by 7 points.

I have a little less than 5 gallons (and 2lbs of honey), so I think the SG is now about 15 points higher, so 0.015 + 1.014 = 1.029.

I'll take an FG reading, but for the sake of argument, if all the honey ferments (i.e., FG goes back to 1.014) then is that another 15 points fermented (2% ABV), giving me an ABV of the final beer of 2% + 7% = 9% ?

 

[dmtaylor]

Yup that's exactly right.

 

[jack13]

Yup that's exactly right.

YES!!!

Thanks.

 

[Vale71]

Except the FG won't go back to 1.014 as the added alcohol is lighter than water and will lower the density, resulting in a lower FG.

 

[jack13]

Except the FG won't go back to 1.014 as the added alcohol is lighter than water and will lower the density, resulting in a lower FG.

I rechecked the hydro reading I had taken from primary while racking. It's moved to 1.015, so with the honey it should be about 1.030 right now.

I'll try to remember to post the FG when it's done.

 

[Mer-man]

I will say also, that for beers with OG over 1.070, use the "alternate" method at Brewers Friend. I had its predictions checked with GCMS at work at it was pretty darn close. The simple method loses accuracy with higher ABV.

 

[jack13]

I rechecked the hydro reading I had taken from primary while racking. It's moved to 1.015, so with the honey it should be about 1.030 right now.

I'll try to remember to post the FG when it's done.

Bottled this today and actually remembered to come back here and post the FG: 1.013, so 2 points below the 1.015 is was at before adding the honey (which had brought it up to 1.030).

So ABV after primary was 7%, plus another 2.2% from the secondary on the honey, for an ABV of 9.2% ( if I've done this all correctly).