Add 1 inch to the finished size so 3" square for you. I always trim down and it does make a difference in matching points. Elinore Burns has a ruler to square half square triangles. You make it like before with the diagonal mark, sew 1/4" either side, cut on the line etc. but instead of pressing it open you use the folded material and place the mark on the ruler along the stitching line for the size you want and then trim the two raw edges, then press open. Instead of 4 sides to cut you only have two. I've used that and a regular square ruler and did the four side cut. Either way is fine for me and works perfectly. I just didn't know if some of you knew about the Elinore Burns Quilt in a Day ruler for half square triangles.