calculating ABV - Home Brew Forums

Register Now!
Home Brew Forums > Home Brewing Beer > General Techniques > calculating ABV

Reply
 
Thread Tools
Old 07-22-2010, 12:51 PM   #1
brazedowl
Recipes 
 
Jul 2009
Fayetteville, NC
Posts: 865
Liked 40 Times on 30 Posts



I've got the general idea of getting the OG and then subtracting the FG and calculating the ABV.

BUT lets say that I get the OG and FG in the primary, and calculate the ABV then rerack onto a significant amount of sugar in the secondary. Do I just measure the OG, measure the FG, calculate again and add the two ABV values?
__________________
In Progress: Blueberry Wine (3 & 5 gallons)
In Progress: Blackberry Wine (5 Gallons)
In Progress: Cran-Grape Wine (5 Gallons)
______________________
"What senses do we lack that we cannot see or hear another world all around us?"

 
Reply With Quote
Old 07-22-2010, 01:04 PM   #2
Bru
Recipes 
 
Jul 2009
Johannesburg, South Africa
Posts: 839
Liked 2 Times on 2 Posts


Im not sure how to do it manually. I use Brewsmith - consider getting it or the free 30 day trial. Otherwise if you say what size batch and how much suger I can work out how much your abv will increase.

 
Reply With Quote
Old 07-22-2010, 01:07 PM   #3
remilard
Recipes 
 
Nov 2008
Kansas City
Posts: 3,654
Liked 43 Times on 41 Posts


No, calculate the OG as it would have been if you added all of the sugar at the start of fermentation, then calculate the actual final apparent gravity, then use the linear approximation of your choice.

 
Reply With Quote
Old 07-22-2010, 01:18 PM   #4
j1laskey
Recipes 
 
May 2010
Boston
Posts: 1,824
Liked 207 Times on 165 Posts


This is how I do it.

I always take reading when I rack to the secondary to give me an idea where my brew is. 99.9% of the time fermentation is completed before I rack to the secondary. I use the secondary for dry hoping/ fruits/ flavors. Before I bottle/keg I take another reading, and 99.9% of the time time is still the same as it was when I rack into the secondary.

OG (pre-primary, wort) - FG (secondary/bottling/kegging) * 131 = ABV

 
Reply With Quote
Old 07-22-2010, 01:39 PM   #5
brettwasbtd
Awesomeness Award Winnner
HBT_LIFETIMESUPPORTER.png
 
brettwasbtd's Avatar
Recipes 
 
Apr 2010
Damascus, MD
Posts: 1,803
Liked 161 Times on 117 Posts


If I understood correctly. You are asking how to calculate a total ABV if you add more fermentables in the middle, right?

I would take an original, and final before racking. Calculate the difference in gravity points (i.e. 1050-1010 = 0040) Then rack onto your sugar, stir, take another sample and maybe you are at 1020 now. Take you final gravity and say you are back at 1010. So your total sugars would now be 0050 and you could multiply that by .131 to get you ABV. The problem here is that you may not have an even dilution of that sugar. So I would go with taking the normal gravities, then weighing out the amout of sugar and using the fermentable ppg number to figure out how many gravity points it is for your volume (5 gallons).

To calculate the sugars you can use this table to see the ppg http://www.byo.com/resources/grains?gtype=5

So for example if you had 1 pound of dextrose in five gallons you would take 1037/5 or really 37/5 which gives you a little over 7 gravity points for your volume. So that should be the increase that you could add to your OG-FG (before racking) differential.

Not sure if this all made sense, but ask questions if it doesnt.
__________________
Shegogue Brew | Pronounced "Shuh∑goo" | http://www.shegoguebrew.com | Videos | Facebook | BJCP Certified Judge B0999
Today's Homebrew News | Searchable Yeast Strain Table! | Basement Induction Brewery Build

 
Reply With Quote
Old 07-22-2010, 05:14 PM   #6
a10t2
Recipes 
 
May 2010
Leadville, CO
Posts: 557
Liked 14 Times on 13 Posts


Quote:
Originally Posted by remilard View Post
No, calculate the OG as it would have been if you added all of the sugar at the start of fermentation, then calculate the actual final apparent gravity, then use the linear approximation of your choice.
+1 - A pound of sugar in 5 gallons will add almost exactly 9 points. Add that to your OG, measure your FG once fermentation is complete, and calculate from there.

Also, (OG-FG)*131 over-estimates over about 6% ABV. There are more accurate correlations if you're interested.
__________________
http://seanterrill.com/category/brewing/
Quote:
Originally Posted by monty3777 View Post
squeeze your sack like it owes you money.

 
Reply With Quote
Old 07-22-2010, 08:20 PM   #7
brazedowl
Recipes 
 
Jul 2009
Fayetteville, NC
Posts: 865
Liked 40 Times on 30 Posts


Quote:
Originally Posted by a10t2 View Post
Also, (OG-FG)*131 over-estimates over about 6% ABV. There are more accurate correlations if you're interested.
Good to know. This is acctually for my blueberry wine. So I have no doubt it'll be up and over 6%
__________________
In Progress: Blueberry Wine (3 & 5 gallons)
In Progress: Blackberry Wine (5 Gallons)
In Progress: Cran-Grape Wine (5 Gallons)
______________________
"What senses do we lack that we cannot see or hear another world all around us?"

 
Reply With Quote
Reply
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Calculating O.G. beforehand? emr454 General Techniques 3 07-05-2010 05:02 PM
Calculating ABV without OG jfkriege General Techniques 15 03-14-2010 09:30 PM
Calculating FG Lucky Dog Brewing General Techniques 3 07-24-2008 03:46 PM
Calculating Efficiency CEMaine General Techniques 2 05-06-2008 12:26 PM
Calculating your malt ” FlannagŠin General Techniques 6 01-31-2007 07:05 PM


Forum Jump