he current quilt that I am making required 136 HST- UGH!!!!! But the direction said to make them by placing 2 4" squares together and sewing 1/4" around the entire edge and cut each way on the diaginol. i had never tried this way but it actuall worked out great!!! I got 4 really good 2 1/2" HST from each square. This was much easier that marking and sewing 2 lines on each square especially when doing so many HST I am sure that there is a chart or formula to determine how big to make the squares for a certain finished size of HST .