Calculating OG after adding water

[njrockpd]

I was brewing last week and after cooling I took a gravity reading of 1.065, which was pretty high for my Schwarzbier. I moved it to a carboy and realized it was about 4 gallons so I added a gallon pitched my yeast and forgot to take a reading.

So my question is if your gravity is 1.065 and you add a gallon of water to it how much with the OG drop? also how do you calculate it? (just in case I run into this problem again)

Thanks.

 

[ACbrewer]

how is your algebra....

in this case 65 points over 4 gallons = 260 points total
so in 5gallons it would be 52 points or 1.052 for the new OG (assuming good mix of water and wort).

So basically it is number of points * volume = total points then total points / new volume = new OG.

Makes sense?

 

[njrockpd]

how is your algebra....

in this case 65 points over 4 gallons = 260 points total
so in 5gallons it would be 52 points or 1.052 for the new OG (assuming good mix of water and wort).

So basically it is number of points * volume = total points then total points / new volume = new OG.

Makes sense?

Is it really that simple? Is that accurate?

Thanks for the quick reply.

 

[ACbrewer]

Assuming I did my math right - yes it is.

Ok more generally.

OG = 1.xxx so the points per volume(V) is xxx.

Thus total points(TP) is V * xxx =TP

If you change V then you can divide out the new V to get the new gravity.

Example. 1 gallon of wort with og of 1.100 is 100 points of malt extract in it would have total points of 100. you then dilute it down to 5 gallons givine 100/5 = 20, so the new og would be 1.020

Example 4 gallons of wort with like a OG of 1.100 (ok really high) thus it has 400 points, which is diluted with 6 gallons of water giving it a 400/10 or 40 points per gallon now for a OG of 1.040

More complecated. 2 gallons with OG of 1.050 and 3 gallons with OG 1.020 would be 100 points for the 2 gallons plus 60 points for the 3 gallons - total of 160 for all 5 gallons = 32 points /gallon and thus OG of 1.032

Hope that helps if you ever need to add more water, or mix to levels of stuff, perhaps you are mixing 2 beers or something in the future.

 

[passedpawn]

C1*V1 = C2*V2

C = gravity/concentration (i.e., 65)
V = volume in gallons

or

C1*V1
------- = C2
V2

65*4
------ = 52
5

= 1.052

 

[njrockpd]

Thanks guys. I really appreciate the help.