How to Piece a Quilt with the Blocks Set on Point

This post is about the differences between a straight set quilt and one with the blocks set on point. It will also teach you how to calculate the size of the corner and side setting triangles for any size quilt blocks.

What is the difference between a straight set quilt layout and one that is on point? For straight set, it is just that. The square blocks are laid out along their straight sides so they look like squares. On point, the quilt is laid out so the blocks are on one of their points and look like diamonds. You also need to finish the ends of each row with triangles. Laying the same blocks out in the two different ways can create very different looks.

It can be intimidating to make a quilt on point because you are working with diagonal rather than straight lines and you have to be more aware of the bias edges of your fabric. It’s not difficult, you just need to learn a few things. The order for piecing the rows will be different. The triangles need to face different ways depending on where they are located on the sides, top/bottom and corners. And, you may need to learn to calculate what size you need for your side and corner setting triangles.

Using some simple illustrations, I will go over the order for piecing rows in an on point quilt. I will also provide the formula for determining what size triangles you need and how to cut them. I will also give you a chart that will provide some triangle sizes already calculated for you, included what you will need for any of the three sizes for the Tiny Nine Patch Challenge.

What is an On Point Quilt?

The center design of the striking tiny nine patch quilt is made from (480) 1-1/2″ nine patch blocks set on point. Did you know that blocks set on point are bigger than when they are in a straight set? They are 1.414 from point to point. That’s one way to increase the size of a quilt without making bigger blocks. Remember this number because we will revisit it when we are talking about the side setting triangle formula.

How to piece the rows of an on point quilt

When you set a quilt on point there will be triangle shaped gaps along the sides of the quilt. You need to fill those spaces with triangles that have the straight of grain along the outside edge. Why is this? You might wonder. That outside edge cannot be a bias edge because that is much more stretchy than the straight of grain. If you have a bias edge, you will have a wavy and distorted quilt.

Side triangles

To cut the side triangles, You will need to first cut a square and then cut that into quarters to yield four triangles. Remember I said that a block on point is bigger than a straight set block? That means if you are making the side setting triangles for a quilt with 3″ squares, you can’t just cut a 3″ square in half diagonally. It will be too small for your quilt. We need to make quarter square triangles. The formula for determining the size of square you need is as follows:

((finished block side measurement) x 1.414) + 1.25 = ____

So, for example, let’s assume the quilt we are working on is made from 3″ blocks. The formula will look like this:

(3″ x 1.414) = 4.242 + 1.25 = 5.492″

Does that look like the kind of number you want to work with when measuring and rotary cutting? No, not at all. So at this step, you want to round up to the nearest 1/8″ increment which for the 3″ block is 5-1/2″. I like to make sure there is a little “fudge” room in my block sizes to make up for variations in cutting and seam allowances so I round up another 1/8″ and would actually cut my square 5-5/8″. Then you cut that square in half diagonally, twice, so it looks like the illustration below. You will need side triangles at the beginning and end of each diagonal row in your quilt.

Always make sure the straight of grain side is on the outside of the quilt.

Corner triangles

You will need four corner triangles for your quilt. No matter how big your quilt is, there will only ever be four corners if it’s a rectangular quilt (squares are rectangles, too). The triangles are cut differently. For this you need a square that is cut the same way as if you were making a half square triangle. There is only one diagonal cut. To calculate the size, add 1″ to your finished block side measurement. For your 3″ finished blocks size you need a 4″ square. Cut as illustrated below.

Piecing the rows and adding the triangles

Illustrated below is a simple four patch quilt set on point. Notice how the blocks are sewn together to form diagonal rows with a side setting triangle at the beginning and end of each row. This applies to ever row except for the ones that end on a corner. It helps to lay out each row to make sure you are doing it right. Your first attempt or two might involve some unsewing but you’ll get the hang of it.

Below is an illustration of sewing the rows together and then the finished quilt center. As mentioned, I like my triangles just a little bigger than the exact size. So, when your quilt center is pieced together, you might need to trim the outside seam allowance to 1/4″ all around. Then, the quilt is ready for you to add borders if you are using them.

Measurements for cutting side setting and corner triangles

So that you don’t have to do the math yourself every time you need setting triangles, I’ve put together a chart for my favorite little quilt block sizes.

Finished Block Size	Cut Squares for Side Setting Triangles	Cut squares for Corner Triangles
1-1/2″	3-1/2″	2-1/2″
2″	4-1/8″	3″
2-1/4″	4-1/2″	3-1/4″
2-1/2″	5″	3-1/2″
3″	5-1/2″	4″
3-1/2″	6-1/2″	4-1/2″
4″	7″	5″
4-1/2″	7-3/4″	5-1/2″
5″	8-1/2″	6″
5-1/2″	9-1/4″	6-1/2″
6″	9-7/8″	7″

If you are making the Tiny Nine Patch Challenge quilt and using nine patch blocks that measure 1-1/2″, 2-1/4″ or 3″ finished, you can find the sizes you need for side and corner setting triangles in the chart above.

Jan Winkel, @winkelacres on Instagram, graciously allowed me to use a picture she took of her partially assembled Tiny Nine Patch. It’s fun to start assembling your quilt as you go because that’s when your cute little blocks lay perfectly flat and you can see how all your fabrics look with your background.

Note that Jan made her side and corner triangles larger so that her side seam allowances are larger than 1/4″. As mentioned previously, this is a very good practice because you can then trim to a perfect 1/4″ seam allowance. And, you don’t have the problem with the triangles being too small.

For more about the Tiny Nine Patch quilt, click here.