Tutorial and Charts for Setting Quilts “on point” (Diagonally)

You’ve finished that wonderful block-of-the-month from last year, and now you have a lovely set of quilt blocks. Now what do you do with them?

One way to “set” your quilt is “on point”. This is when you set your blocks on the diagonal, as you can see with my quilt, September.

September quilt from Quilt Batik! ©2012 Cheryl Brown/That Patchwork Place

The confusing part of “on point” quilts is the setting triangles and and corner triangles. This post should help with that! When constructing an “on point” quilt, you lay your blocks out on the diagonal. Then you need two types of triangles: setting triangles, and corner triangles.

The setting triangles are the triangles along the sides and the top and bottom. These are made by cutting a square into quarter triangles. (Cut along the diagonal, then the opposite diagonal.) This provides a straight grain along the edge of the quilt.

The corner triangles are the 4 triangles in the corners. (Obviously!) These are made by cutting a square into half-squares triangles (Cut along one diagonal.) This provides 2 sides of the triangle on the straight grain. Here’s a diagram:

To make it really simple, I’ve compiled a chart to help you find the size of square you need for each of these triangles, based on the finished size of your quilt blocks.

Click to download a printable version of this chart.

You can buy tools to help you make setting and corner triangles. One tool I have is from Marti Mitchell; the Diagonal Set Triangle Ruler. Another is the Flip n’ Set ruler from Darlene Zimmerman.  These have the advantage of using a strip of fabric instead of a large square that you quarter.

Diagonal Set Triangle Ruler from Marti Mitchell and Flip n’ Set from Darlene Zimmerman.

Sometimes you need to know the measurement of a block set “on point” if you’re designing a quilt, or setting one differently from the pattern. Here is a simple chart that shows the diagonal measurement of a block:

Click to download a printable version of this chart.

You can use math to figure the diagonal size of your block, if it is smaller or larger than the chart. There are two methods.

The first method is to multiply the block size by 1.414235, and then round. For example: If your block is 12 1/2″ square, you multiply 12.5 x 1.414235 = 17.6779, and round to 17 3/4″.

The second method is to divide the block size by 2.4, and then add the block size to the result. For example: If your block is 12 1/2″ square, you would use the following formula:

Block size (12.5) ÷ 2.4 = 5.21; Then: 5.21 + Block size (12.5)= 17.71; round to 17 3/4″.

Hopefully this will help you when you want to set those quilts on point for a new look!