Sugar Substitutions

I am looking at brewing an Irish Stout recipe that calls for 1lb of corn sugar to be added to the boil.  I’d like to substitute dark molasses for at least part of the corn sugar, I’ve used molasses in a scotchish ale before so I like what it brings to the flavor.  Any idea of how much I should reduce the corn sugar if I add 8 fluid oz of dark molasses?

Google “on-line beer recipe calculator” & type in your recipe as is.  Note what the OG is, then add your mollases and reduce the sugar amount until you get back to that OG.

My database indicates that sugar has 46 points per pound per gallon while molasses has 36 points per pound per gallon. If you add 8 oz by weight (not volume) of molasses that should provide 18 points per gallon, which would be the equivalent of 18/46 = 0.4 lbs = 6.4 oz of sugar.

Thanks for the suggestions, I will check out the online calculator as well.  It might be a bit before I am ready to do the stout recipe but this has been helpful in the preparations.