Calculating stepped sugar additions

[wetdog]

I'm experimenting with a kit lager to try and 'pump up the volume'

I fermented out on the supplied yeast and then racked into a second FV.
I then added more sugar and pitched in a champagne yeast.

I let that ferment out and have now added more sugar.

I've taken gravity readings at the start and end of each mini ferment but how do I use this collected info to calculate the final gravity?

I believe the way to do this was printed in CJ Berry's book on winemaking but I can't find my copy for love nor money. anyone got the magic formula?

[BlackBag]

Old post this I know (note to self - find some work to do instead of going through the unanswered posts section) but I was wondering if this formula appeared anywhere.

[psd123]

Got this in my coopers stout not sure if it is what you want OG-FG/7.46+0.5= approx%.

Cheers Paul

[wetdog]

Old post this I know (note to self - find some work to do instead of going through the unanswered posts section) but I was wondering if this formula appeared anywhere.

From what I can gather you take the OG before pitching, then take another reading days later and note how many points its dropped, eg 10.
next you add sugar and take a new higher reading. after a few days check again and see how many points its dropped, eg 6.
now add the 6 to the 10 to get 16 points. you can keep adding sugar and adding the points dropped until the brew is fermented out and whatever figure you have at the end is what you use to work out the final gravity

[BlackBag]

Cheers. Thought it might be something as simple as that, but one thing this homebrew malarkey has taught me is never to expect the obvious