Adding Varying Gravities - How Do I Do It?

[CenturyStanding]

Hey everyone,

I have a quick question. One of my beer recipes is a Belgian Strong Ale thats blended with a small quantity of Sangiovese concentrate. Anyway, I've done it before and the beer has turned out fantastic, but this time around I'm going to try to get slightly better attenuation. Instead of boiling the wort, blending it with the concentrate, and pitching the yeast, I'm going to start fermentation on the wort alone, then feed the concentrate to it incrementally as fermentation progresses (as some do with sugar additions and such for the same reason).

Anyway, my question is, when incrementally feeding sugar like that, how does one calculate the actual original gravity to accurately gauge the ending alcohol content.

If the concentrate is 68 brix (1.336 O.G.) and I'm adding 1 pint to 5 gallons of beer with an O.G. of 1.060, what is the ACTUAL O.G.?

 

[TipsyDragon]

(OG1*volum1 + OG2*volume2)/(volume1 + volume2)

 

[david_42]

The simplest way is to convert to points and then back to gravity. 5 gallons at 1.060 is 300 points, 1 pint at 1.336 is 42. So, the combination is 1.068, ignoring the pint volume.

(verbalization of above equation)