Originally Posted by
PaperPrincess
The calculation for making HST is that you add 7/8" to the FINISHED size. So to make 4" finished HST, you would add the 7/8, which gives you 4 7/8. Since most folks don't really want to cut odd size squares, they round up the 7/8 to one inch, sew and then trim and square them down a bit to 4.5" (which finish at 4"). Since you trim all sides of the finished patch, you are only trimming off 1/16". Just a sliver.
So basically, if you want to make 4" finished HST, you cut 5" squares.
That is how I would do it. We tend to sometimes get away from the math that is required with things such as cutting from strips and using Thangles where the math is embed into the product. Good Luck.