Specific Gravity Question

Let's say I have 4.5 gallons of wort with an specific gravity of 1.064. If I were to add .5 gallons of water to that wort before adding the yeast, what is the new specific gravity and O.G. of this beer? Bonus points if you show your work.

Thanks HBTers!

1.058

I didn't do any hand calculations - there is a dilution tool built into Beersmith. You should check it out - you can download it for free and use it during a trial period before purchasing it. Its really great, and Brad, the guy behind it, provides a great service. So many uses, including your question.

If you start with 4.5g at 1.064, you have 288 gravity points. That's 4.5 (gallons) * 64 (the meaningful part of 1.064)
Now you add 0.5g water (with an OG of 1.00) so you have 5 gallons, but the same number of gravity points, so divide 288 (gravity points) by 5 (total gallons) and you get 57.6 Convert that back to specific gravity, and you get 1.0576
Consider a gravity point as (the specific gravity - 1.000) * 1000 if you want to be mathematically correct.

-a.

Thanks Pappers and ajf!

Pappers said:

1.058

there is a dilution tool built into Beersmith. You should check it out - you can download it for free and use it during a trial period before purchasing it. Its really great, and Brad, the guy behind it, provides a great service. So many uses, including your question.

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Actually, I've paid for a registered copy of BeerSmith, and I agree that it's really great. Every time I use it I learn something new. I didn't know about the dilution tool, so thanks for the heads-up!