Calculating ABV

[winenewby]

I started a new batch of blackberry wine following a recipe that I used before. After mixing the crushed berries and the rest of the ingredients my starting SG was 1.050.
After 7 days the SG was 1.010.
I strained the pulp and added cooled water/sugar mixture per the recipe and the SG is now 1.040. I moved it to the primary and in another 7 days I will add another water/sugar mixture and the SG will rise again.
How do I calculate the ABV with multiple SG readings that this recipe calls for?
I used this recipe in the fall and the wine was great but I had no clue what the ABV was.

 

[smurfe]

I may be off but I would calculate it as follows. It is basically using a points scale. Your SG is 1.050 and it ferments down to 1.010. That is 40 points. You raise the ABV to 1.040 from 1.010 that is 30 points. lets say you ferment down to 1.00. So I would figure this out as essentially the same as an SG of 1.070 fermenting down to 1.000 so I would take 1.070 subtract 1.000 and multiply by 131.

1.070 -1.000 = .070 x 131 = 9.17%

 

[Malkore]

smurfe is absolutely correct. since you know you're adding X number of gravity points, you can just pretend the original gravity was 1.070 (or whatever the added points comes out to).

 

[Wade E]

I could be wrong but the way I always do it is to add what ever I have upped the sg and add that to my original sg making it 1.080 (1.050 +.030) and then subtract my finished gravity from that. So tmy way comes out as 1.080 - say 1.000=.08 x 131.4 = an abv of 10.512 %

 

[smurfe]

You read both ways Wade. I know in Beer everything is in Gravity Points and is figured the way I do it. When I figure a recipe in beer I add the gravity points of each fermentable grain or adjunct to figure my potential OG (SG) and then the potential attenuation of my yeast. I did do a Port once which you ferment down and then add sugar to boost it up and ferment further. I was told both ways but told the way I do it a lot more times so I always went that way.

 

[winenewby]

Thanks, excellent info as usual. I'm glad it's not too complicated.