Looking to figure out how to calculate my new ABV. OG was 1.045, looking for FG of 1.005, stalled out at 1.014. Added yeast starter, which brought gravity to 1.019. Any help would be most appreciated. Thanks.

It would be a bit of a guessing game unless you have more info. The reason being is that a starter’s gravity could be somewhere between its OG and FG when you put it in.

If you know your starter’s OG and volume, it’s much easier….

New OG = ((original OG in gravity points * original volume) + (original OG of starter wort in gravity points * original volume)) / beer volume + starter volume

If this was a 5 gallon batch OF 1.045 with a half gallon starter at 1.060 it would calc like this:

New OG = ((45 * 5) + (60 * 0.5)) / 5.5 = 46.3 or rounded 1.046

Once you hit final gravity you can calculate the abv with the new OG and the measured FG.

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