Originally Posted by MadQuilter

The HST on the right side is the correct size because you have the 1/4" for the seam allowance. The other HSTs do not have the seam allowance so your measurements seem to be off on those. I would suggest you take the block apart and measure each piece to see what went wrong - then duplicate the dimensions from the correct one. HSTs are not the easiest for a newbie.

Hang in there.

How do you sew your HSTs? I generally cut my squares 1" larger than the finished HST size. Then I draw a sewing line 1/4" from the center in each direction. I sew on those lines and then cut the HST apart down the center. Press open and trim to the correct size. It IS a little bit more work but my HSTs don't lose points.