Originally Posted by
Donnamarie
The correct formula is to add 7/8" to the finished size. I always find it better to add an 1" (or a little more) and then you have more wiggle room. You have a little more work to do because you have to square them up afterwards, but I find I have better results this way. Good luck!
I find adding one inch to the finished size works much better for me, too.
And I have to trim very very little off the HST units. I don't know what happens when I add only 7/8 inch, but the units almost always turn out skimpy. And that's even when I make the seams a click or two narrower than for the seams for straight pieced seams.