Must Gravity

[Dark_Ale]

How do you calculate the amount of sugar to desired gravity?
If you have 4 gallons of must at 1.070 and you want to end up with 5 gallons of 1.090 how do you figure the sugar and water? I'm sure this has been asked before I did'nt find it in searches.

 

[Jim-wy]

I'm guessing at this and with the help of a different post: https://www.homebrewtalk.com/f25/calculating-gravity-101641/

I was helped with a similar question earlier today, here's my thought:

4gal(1.070sg) + 1gal('x'sg) = 5gal(1.090)

4(1.070) + 1x = 5(1.090)

4.28 + x = 5.45

x = 1.17, you want your additional gallon with SG of 1.170

If 1# sugar added to 1 gallon of water sets the SG to 1.046, it has raised the SG by .046 and you want to raise it by .17; divide .17 by .046 for # of sugar. 0.17/.046 = 3.7# sugar to 1 gallon water for SG 1.170.


Hopefully somebody who knows will chime in, but I think that should work.

I hope I didn't turn something simple into something difficult... Best Wishes!

 

[DMartin]

That's exactly how to calculate it, and your math checks out. I was surprised now much math and chemistry there was to relearn when I started brewing, but it is useful to be able to do simple algebra.

 

[Jim-wy]

That's encouraging - good deal!