Personally, I cut my squares 1 inch larger than the finished HST needs to be, sew, cut, then trim to desired size. I just find it easier that way.

beverly

I do as Beverly does, but the rule is add 7/8 inch to the finished measurement for a half-square triangle, and 1.25 inches if you're going to make a quarter-square triangle.

Thank you both - 1" larger is very easy to remember.