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I added 1 lb of Lactose to a 5 gallon batch of Porter. I'd read that this would account for up to 0.007 of additional gravity.

When calculating the true ABV, should I subtract 0.007 from the actual hydrometer reading?

For example, if my OG hydrometer reading was 1.067 and my FG is 1.029 would by true ABV be...

5.1% to represent 1.067 (OG) and 1.029 (FG)

or

6.0% to represent 1.067 (OG) and 1.022 (FG) [1.029 - 0.007 lactose corrected]?

Raenon

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If you measured the OG with the lactose in it, you need to subtract the 0.007 from the OG as well as the FG if you wish, but 1.060 OG -> 1.022 FG is still 5.1% ABV

It doesn't matter how many points you're left with, it matters how many fermented. In this case, you have 38 gravity points that fermented out, which will be 5.1% ABV. Even if you started with a 1.138 and only fermented to 1.100 (by some strange use of nonfermentables), it'd be 5.1% ABV.

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Thanks! Appreciate the info.