Yet another gravity question.

[vw addict]

So my second day of all-grain went much smoother. I slowed the sparge way down and I think I got really good efficiency. Problem is when I took a gravity reading I was getting 1.072, I was supposed to be around 1.060. When I got the wort into the carboy I found the problem, I was only at 4.5 gallons. I added 1 gallon of water to the carboy to bring it to the planned 5.5 gallons. My question is what would another gallon of water do to the gravity reading? I know I should have just took another reading, but it was a long day and I didn't.

[toneyc]

According to Promash's Wort Diluted with Water Calculator, your new gravity should be 1.059.

:)
Toney.

[vw addict]

wow, a wort dillution calculator really exists? Thanks man. Looks like I hit my target gravity. Just checked on the fermentor and it's bubbling away. Good way to start a Monday off.:D

[HogieWan]

Originally posted by vw addict [/B]

ProMash and BeerSmith both have them

[paulcgi]

If you really care about the math:
the amount of sugar in wort doesn't change with boiling. You are changing the dilution of it. It's really easy to calculate gravities even if you don't have one of the aforementioned software packages.
let's take your example so you can see the "formula" for it
(it just uses the gravity points, so just the 72 from 1.072)
gravity times volume = total points
total points divided by new volume = new gravity

70 * 4.5 = 324
324 / 5.5 = 59

so new gravity equals 1.059.. this is a handy method too to know during brew day if you are going to hit your gravity or not. If you really need to be at a specific OG, you can then calculate how much extract or water you need to add to hit it.