ABV calculation question

[BaysideBrewer]

I brewed an extract recipe but in addition to what the recipe called for I added a # of honey with 5 min left in the boil. Unfortunately at the time of boil I didn't have a hydrometer so I didn't get a legit OG reading. The OG of the recipe w/o the honey was 1.052.

I bottled today and took the FG reading and got 1.02...I was under the impression that to calculate abv = (FG-OG)×131. Clearly I can't have a negative abv but was just curious if I'm doing something wrong. Not having the legitimate OG doesn't help and could be the issue, but I would think the addition of the honey (more fermentable sugar) would make it more alcoholic. ...not negative . Would the honey affect the OG value to be significantly different?

Good news is the sample from hydrometer tasted good...juat curious as to abv

 

[ArcaneXor]

You have them switched. It's (OG-FG)*131.

Most honeys are somewhere in the range of 32 to 39 pppg. So assuming something in the middle of that range your OG should be roughly 1.052 + (35/5) = 1.059.

 

[BaysideBrewer]

Great thanks! I figured I had something switched but the value for the honey edition is really helpful.