### Author Topic: Pre-boil gravity calculations.  (Read 1510 times)

#### mnstorm99

• Cellarman
• Posts: 98
##### Pre-boil gravity calculations.
« on: March 27, 2010, 08:53:38 AM »
Alright, I know this wouldn't be that hard to figure out...but my brain is failing me this morn.  What is the best way to figure approximate OG from my pre-boil SG?  Or...is there a calculator?
*Tapped:
Peach/Raspberry Ale 4.5%/18IBU (6/6/10)
Golden Promise IPA (Keg #2) - 5.8%/73IBU (7/3/10)
Jason's Ball & Chain - 6.4%/63IBU (7/17/10)
All His Merry Men - 4.9%/23IBU (8/1/10)
Citra Amber Ale - 4.8%/23IBU (8/1/10)

#### denny

• I must live here
• Posts: 10724
• Noti OR [1991.4, 287.6deg] AR
##### Re: Pre-boil gravity calculations.
« Reply #1 on: March 27, 2010, 09:42:41 AM »
(SG*boil volume)/final volume=OG
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

#### mnstorm99

• Cellarman
• Posts: 98
##### Re: Pre-boil gravity calculations.
« Reply #2 on: March 27, 2010, 09:58:25 AM »
(SG*boil volume)/final volume=OG

Thank Denny, this is what I thought, but my math is really not working...I must be stu, stu, stupid today

So in my case I have:
(SG 1.040 * BV 6.5)/FV 5.5 = OG 1.229
This isn't right.
*Tapped:
Peach/Raspberry Ale 4.5%/18IBU (6/6/10)
Golden Promise IPA (Keg #2) - 5.8%/73IBU (7/3/10)
Jason's Ball & Chain - 6.4%/63IBU (7/17/10)
All His Merry Men - 4.9%/23IBU (8/1/10)
Citra Amber Ale - 4.8%/23IBU (8/1/10)

#### denny

• I must live here
• Posts: 10724
• Noti OR [1991.4, 287.6deg] AR
##### Re: Pre-boil gravity calculations.
« Reply #3 on: March 27, 2010, 10:02:30 AM »
(SG*boil volume)/final volume=OG

Thank Denny, this is what I thought, but my math is really not working...I must be stu, stu, stupid today

So in my case I have:
(SG 1.040 * BV 6.5)/FV 5.5 = OG 1.229
This isn't right.

I shoud have been more specific...you leave off the "1", so it's really ((SG-1)*BV)/FV.  In your case it would be (40*6.5)/5.5=47.27
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

#### mnstorm99

• Cellarman
• Posts: 98
##### Re: Pre-boil gravity calculations.
« Reply #4 on: March 28, 2010, 03:32:14 AM »
Yep, gravity points...not hydrometer readings, that's what I was doing.

Thanks
*Tapped:
Peach/Raspberry Ale 4.5%/18IBU (6/6/10)
Golden Promise IPA (Keg #2) - 5.8%/73IBU (7/3/10)
Jason's Ball & Chain - 6.4%/63IBU (7/17/10)
All His Merry Men - 4.9%/23IBU (8/1/10)
Citra Amber Ale - 4.8%/23IBU (8/1/10)