Generally, it's volume for volume. As in 1/2 c. sugar = 1/2 c. Splenda. I've
never used Splenda as the only sweetener and have always combined it with sugar. So this was a first for me.
I have the Lemon Poppyseed Cake in the oven right now with 1 1/4 c. Splenda and 1 c. sugar. We'll see.