Can I substitute butter with coconut oil..if I can,how much?

I substitute one cup LESS two tablespoons of coconut oil for one cup of butter. This has worked for all my baking recipes except for shortbread. Shortbread needs butter.I have not tried this with pound cake. This substitution makes for more tender cakes, crispier cookies, and lots of compliments.

I thought the same thing when I originally saw this recipe. I believe butter and coconut oil differ in their percentages of fat, and I'm not sure of the proper substitution. But if I were taking a crack at it, I'd probably cut back on the coconut oil slightly--maybe by 1/4 cup. Again, this is not at all tested or science, so hopefully someone else will weigh in.