Dilution calculation?

[whoaru99]

This should be simple but I'm having a brain fart...

I have 750ml of 14.5% alcohol solution that I want to cut back to 10%.

How much water to add?

I come up with 337.5ml. Seems like a lot so not sure that's correct.

 

[DBhomebrew]

You got it right. Lots of ABV dilution calculators online.

 

[jerrylotto]

The calculation is simple 750ml * 0.145 = 108.75 ml pure alcohol, so a10% solution of that would be 1.0875 liter volume.
1087.5 ml - 750 ml = 337.5 ml water to be added to make the desired volume and concentration.

 

[whoaru99]

I ended up taking it down to 8%.

14.5 - 8 = 6.5
6.5 × 750 = 4875
4875 / 8 = 609.4ml water added

 

[Broothru]

The calculation is simple 750ml * 0.145 = 108.75 ml pure alcohol, so a10% solution of that would be 1.0875 liter volume.
1087.5 ml - 750 ml = 337.5 ml water to be added to make the desired volume and concentration.

I’ve never trusted my math skills, especially in public, so I’m glad Dr. Chris Smith included so many easy calculators in BeerSmith. I recently brewed a Kolsch with a target ABV of 4.6%. My target OG was 1.045 but came out at 1.050, which would have come out above BJCP guidelines for Kolsch at @ 5.2%.

I used the dilution calculator and the numbers (and the finished beer) came out exactly at the targeted 4.6%. I’m the poster child for “Calculators for Dummies”, so either I was really lucky or his calculators are really good.