Volume of 150g of Sugar?

I'm going to be baking some cookies this weekend, and the recipe that I have is in weights, not volume. I'm going to be substituting Splenda and don't have the heavier granulated kind. I'm not too worried about losing a bit of bulk to my cookie dough, but I don't want to get it overly-sweet. Obviously substituting in 150g of the more 'feathery' original Splenda would be out of the question. I don't keep sugar on hand so I can't gauge how much Splenda to use for equal sweetness. I'm thinking that I'm looking at about 1/2 cup? If someone could verify this for me, I'd be most appreciative!