How to Make Setting Triangles

Time to get the Calculator! This involves some Formulas! I'll show you how to do the math, and include some pre-calculated sizes below!

CORNER SETTING TRIANGLES: 

Finished block size divided by 1.414, plus .875  for seams, rounded up to the nearest 1/8" Make SQUARE this size and cut it in half once on the diagonal to make two corner half square triangles.

SIDE SETTING TRIANGLES: 

Finished block size multiplied by 1.414, plus 1.25 for seams, rounded up to the nearest 1/8" Make SQUARE this size and cut in half twice on the diagonal to make four side quarter square triangles.
EXAMPLE:

To accompany a finished 12" block, for the corner triangles...

12 / 1.414 = 8.489 + .875 = 9.364  or 9-3/8" square, cut in half once diagonally

and for the side triangles...

12 x 1.414 = 16.968 + 1.25 = 18.218 or 18-1/4" square, cut in half twice diagonally
 

Common Setting Triangle Sizes

Finished Block Size

Side Triangles

Corner Triangles

4"

7"

3-3/4"

5"

8-3/8"

4-1/2"

6"

9-3/4"

5-1/8"

7"

11-1/4"

5-7/8"

8"

12-5/8"

6-5/8"

9"

14"

7-1/4"

10"

15-1/2"

8"

12"

18-1/4"

9-3/8"

14"

21-1/8"

10-7/8"

15"

22-1/2"

11-1/2"

16"

23-7/8"

12-1/4"
Oct 2002 Marcia Hohn