Calculating abv

Discuss all aspects of fermentation
Post Reply
User avatar
mark1964
Tippler
Posts: 10
Joined: Fri May 08, 2020 10:26 am
Location: Hessle

Calculating abv

Post by mark1964 » Fri May 08, 2020 3:50 pm

Can anyone help with calculating abv pre ferment. I've forgot how to do it 😅

guypettigrew
Even further under the Table
Posts: 2626
Joined: Mon Mar 22, 2010 7:10 pm
Location: Christchurch, Dorset

Re: Calculating abv

Post by guypettigrew » Fri May 08, 2020 4:15 pm

It's about 10% of the OG. In other words, a wort of 1.050 will give you a beer of about 5%, probably a bit less.

Graham Wheeler's beer engine will give you a more exact figure, but is all depends on the finishing gravity. You can find it on this page.

Guy

User avatar
mark1964
Tippler
Posts: 10
Joined: Fri May 08, 2020 10:26 am
Location: Hessle

Re: Calculating abv

Post by mark1964 » Fri May 08, 2020 4:44 pm

Thanks

richard080561
Piss Artist
Posts: 199
Joined: Thu Jan 21, 2016 12:02 am

Re: Calculating abv

Post by richard080561 » Fri May 08, 2020 4:45 pm

There's an easy to use calculator on Brewer's Friend, you enter the SG and OG .
Richard M
Cardiff

nickjdavis
Steady Drinker
Posts: 59
Joined: Thu Apr 11, 2019 3:10 pm

Re: Calculating abv

Post by nickjdavis » Sun Jun 28, 2020 10:38 am

OG minus SG times 131 will get you pretty much as close as you need to be.

e.g.

1.050 - 1.010 = 0.040

0.040 * 131 = 5.24 (%)

User avatar
vacant
Even further under the Table
Posts: 2167
Joined: Mon Aug 20, 2007 5:39 pm

Re: Calculating abv

Post by vacant » Sun Jun 28, 2020 2:29 pm

Plus any priming sugar.

100g in 23 ltr converts to CO2 plus alcohol adding about 0.5%.
I brew therefore I ... I .... forget

User avatar
Kev888
So far gone I'm on the way back again!
Posts: 7701
Joined: Fri Mar 19, 2010 6:22 pm
Location: Derbyshire, UK

Re: Calculating abv

Post by Kev888 » Mon Jun 29, 2020 11:17 am

As above, you can guess it based on the difference between apparent OG and predicted FG, plus any priming. The FG can obviously vary quite a lot, depending on the type of yeast and fermentability of the wort, so the accuracy of the ABV prediction will depend on how closely you can predict the FG. Thats something I'm not brilliant at with new recipes/brews, I can often be a percent or so out unless I've tested them before or done a forced-ferment.

(Once you have the actual FG then there are more detailed formulae, that would be accepted for duty calculations. It is still a similar principle, but the values change slightly according to different OG ranges and so on).
Kev

Post Reply