Setting a block on-point can provide an innovative look to a familiar block. It’s amazing how something as simple as rotating a block can transform a nice setting into a spectacular setting. Many blocks adapt very well to a diagonal setting, especially the flower blocks.

Experiment with diagonal sets, you’ll be amazed with the results!

When a block is turned on-point you also require “filler” or setting triangles on the sides and at the corners. It is very important that the outside edge is on the straight-of-grain, therefore the size of square to cut and the cutting procedure is different for both triangles.

The size of the “filler” triangles will depend on the finished block size.

There is a very simple mathematical formula to calculate the exact size of squares to cut. You don’t have to guess, do trial and error or cut triangles too large and trim to size later.

Corner Triangles

Corner triangles are made from a square, cut once on the diagonal to yield two corner triangles.

Determine the finished block size, do not include seam allowances in the calculations.
Divide this number by 1.414. You will definitely need a calculator for this!
Round up to the nearest 1/8 of an inch. (Refer to the Decimal Equivalent
chart at the bottom of the page.)
Add 7/8" (.875") to this measurement. The result of the calculations is the size
of square to cut.

Calculating the size of square to cut to yield 2 corner triangles for a 12" finished block:

(Do all the calculations in decimals, it’s easier than converting fractions to decimals.)

12 ¸ 1.414 = 8.49. Round up to nearest 1/8" = 8.5.

8.5 + .875 = 9.375 or 9 3/8". This is the size of the square to cut.

Cut two squares 9 3/8", cut both squares once on the diagonal, to yield 4 corner triangles .

It is not necessary to memorize the decimal equivalent chart, just remember that 1/8 is .125. Convert the fractions to 1/8’ths and multiply .125 by the enumerator (in the fraction 5/8, 5 is the enumerator) 5 x .125 = .625

Decimal Equivalent Chart
1/8 = .125
¼    = .25
3/8 = .375
½    = .5
5/8 = .625
¾    = .75
7/8 = .875

Side Triangles

Side triangles are made from a square, cut diagonally in two directions to yield four side triangles.

1. To determine the size of square to cut multiply the finished block size by 1.414.

2. Round up to the nearest 1/8" and then add 1 ¼" (1.25).

Calculating the size of square to cut for side triangles for a finished 12" block:

12 x 1.414 = 16.97, round up to the nearest 1/8" = 17.
17 + 1.25 = 18.25 or 18 ¼".
Each 18 ¼" square will yield 4 side triangles. How many 18 ¼" squares to cut
will depend on the amount of “filler” side triangles required.