PPG calculation question - check my math please

[InspectorJon]

I have an imperial stout I want to add some final gravity points to. It has finished at 1.029 and I want it to be 1.040. It’s a milk stout and I have not added any lactose yet. The original beer we are trying to emulate also reportedly has some maltodextrin in it. I’m hoping someone will check my math and logic on this for me.

I have 3 gallons to bring up to 1.040 and it’s 1.029 now, so I need to add 11 PPG. For 3 gallons that would be 33 total points, correct?

Lactose has 41 PPG. If I divide that by 16, I get 2.5625 points/oz/gallon (POG) so 10 oz would add 25.625 total points.

Maltodextrin has 39 PPG divided by 16 = 2.4375 POG X 3 = 7.3125 points for a 3 oz addition.

25.625 + 7.3125 = 32.9375 or 33 total points added to the three gallons. This looks right to me. Thanks for any confirmation or corrections.

I am working on this Abraxas Imperial Mexican Chocolate Stout recipe over here

 

[VikeMan]

Your math is sound. One little thing... the lactose and maltodextrin will also add volume, so your FG would be slightly lower than what you're computing. But it's probably not worth worring about in this case, i.e. if you're not also adding water.

But, keep in mind that if you add water (to dissolve/boil/sanitze the lactose and maltodextrin), you'll be increasing volume even more.

 

[duffy5018]

Am I missing something? You have 3 gallons, right? 10 oz lactose + 3 oz maltodextrin per single gallon would give you about 33 total points.
So, you'd need 30 oz lactose and 9 oz maltodextrin to raise 3 gallons to riase 33 points.

EDIT:
Checked my/your math on brewer's friend and yeah, 10oz lactose and 3oz maltodextrin would give you about 11 points in 3 gallons

 

[VikeMan]

EDIT:
Checked my/your math on brewer's friend and yeah, 10oz lactose and 3oz maltodextrin would give you about 11 points in 3 gallons

...which is what he wants to do.

 

[duffy5018]

...which is what he wants to do.

Yup. I was missing something. Got hung up on the math I missed the problem