I've just finished a quilt top in which I placed the squares on point, necessitating figuring the size of the triangles that went around the edges, to fill in between the on-point blocks, AND also the ones to complete each corner. Many may know how to do this, but thought I'd post the method I use, which makes life easier "on point". I'm somewhat math challenged, but even I can do this one!

The top is made of a bunch of 'basket' squares I found at an antique shop...these weren't enough for a queen sized quilt for our daughter, so I augmented them with some 'shirting' fabric squares. The squares were hand pieced, but somewhat irregular in size, so I sashed each with a dark fabric so I could then cut them to the same size...in this case, 9"...this makes the squares uniformly sized, but the sashing 'off' here and there. But, I don't think it'll be noticeable when viewing the quilt as a whole. I'll post a pic later.

for setting triangles, multiply the finished size of the block by 1.414 and then add 1 1/4 (or 1.25) cut a square that size and cut into fourths, corner to corner. (you get 4 correctly sized triangles from one square done in this manner).

for example, with a 6 inch block (finished size);

6" X 1.414 = 8.484 + 1.25" = 9.737 (or in quilters' language, 9 3/4") So you would cut a9 3/4" square and then cut corner to the diagonal corner twice...this gives 4 side, or setting triangles.

( to find the corner triangles, divided the finished block size by 1.414 and add 7/8"...cut a square and slice once, from corner to corner)

My husband brought me a large square, which is great for the corner triangles, to get them just right.