Adding cane sugar to fermentation

Can someone just reaffirm my math or tell me I am wrong please?

I brewed up a tripel recipe which called for a OG of 1.081. I did not add the cane sugar because I didn't want my yeast to get lazy so i am going to add it tonight the second full day of fermentation.

I had an OG of 1.061 w/o the sugar. I am planning on adding 2.5# of sugar as the recipe calls for.

Am I correct in my math that the sugar will have .115 gravity points (46x2.5), which then 115/5 gallons = .023 thus giving me a true OG of 1.084?

Thanks, I just wanted to make sure I am understanding Palmer's book correctly

I usually just add into my brew software as if it was in the boil. That will give me what the OG should be. THen if you take it out that will give you the Og without it.

Right but I didn't hit the OG that beersmith thought I would hit, so how would I adjust it. Beersmith says that my recipe will end up with 1.089 and Jamil says 1.081.

I am trying to figure it out based on what my measured OG was and then use the ppg of sugar to figure it out.

Yep, calculation looks right to me.

Math looks good (of course assuming you have a true 5 gal in there).