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Old 09-12-2010, 04:36 PM   #1
solaceBrewing
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Default Calculating combined SG of 2 separate volumes

Sometimes I collect more wort than my pot can hold and need to use 2 pots. But then I want to know what the combine SG is of the total wort so I can calculate efficiency.

I finally figured this out the other day, so here's a way to do it for anyone else that runs into this situation:

1. Measure SG and volume for each pot. For example, lets say I have pot A which is 5 gal at 1.068 and pot B with 2 gal at 1.40.

2. Convert both of these SG readings to ppg (points per gallon), by taking away the "1." of the reading (or subtract 1 and multiple by 1000). So we have pot A with 68 ppg and pot B with 40 ppg

3. Multiple each ppg value by the volume in gallons to get gravity points. Pot A is 340 gravity points and pot B is 80 gravity points.

4. Add the gravity points of each pot together. Pot A + pot B = 420 total gravity points

5. Divide total gravity points by the total volume in both pots. 420 points / 7 gal = 60 ppg

6. Convert back to SG (divide by 1000 and add 1). 1.060 is the combined specific gravity of both volumes.

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Old 09-12-2010, 05:04 PM   #2
Fletch78
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Maybe you can help me. I have a pre-boil volume of 6.5 gallons and gravity of 1.040 (adjusted for temp). I have a post-boil volume of 5.25 gallons. What is the new gravity?

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Old 09-12-2010, 05:16 PM   #3
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Quote:
Originally Posted by Fletch78 View Post
Maybe you can help me. I have a pre-boil volume of 6.5 gallons and gravity of 1.040 (adjusted for temp). I have a post-boil volume of 5.25 gallons. What is the new gravity?
boil off of 1.25 gals with 1.040 SG pre-boil will be 1.049

Easiest way to do these calculations is to go get a copy of ProMash brewing software. It will do everything for you
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Old 09-12-2010, 05:18 PM   #4
Fletch78
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I found this also... thanks!

http://www.homebrewtalk.com/f36/conv...st-boil-41994/

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