How to Make a Triangle in a Square Quilt Block

Posted by Elaine Huff on

The Triangle in a Square block can be constructed a few different ways. While simple, the block can be tricky so let's learn how to successfully piece it together.

triangle in a square quilt block

This block is also called Peaky and Spike and usually is used as a unit in another larger quilt block. There are three different ways this block can be constructed - by templates, paper piecing, and by special rulers. Let's look at paper piecing and rulers!

Paper Piecing Requirements for a 4" Finished Triangle in a Square Quilt Block:

  • Template: 1 per block (you can download a template HERE) Cut out with an additional 1/4" or so around each template
  • Light/White: 1 - 5" square (approximate)
  • Dark/Purple: 2 - 3" x 6" rectangles (approximate)

requirements for block

Sewing Directions:

Step 1:

Pair up one template with the Light/White 5" square - WRONG sides together. 

triangle square 1

Step 2:

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Either pin them together in the middle or use a fabric glue stick. I really like the Roxanne Glue Stick shown below. This glue dries clear, washes out, is odorless, acid-free, and non-toxic, AND fabric is easy to reposition if necessary. 

roxanne glue stick

Step 3:

Position one of the Dark/Purple 3" x 6" rectangles on top of the Light/White square (right sides together). Make sure the rectangle is positioned so that when you fold back the rectangle after sewing, it will cover the Light/White square corner. Glue or pin together.

triangle square 3 2

Step 4:

Turn over and sew on the diagonal line of the template. Shorten your stitch length to about 1.5 so that the paper will be easy to remove after you've completed sewing the block.

triangle in a square 3

Here's picture from the other (right) side after sewing the first seam.

triangle in a square 4

Step 5:

Fold back the template paper along the seam line and trim the seam allowance as shown in the picture below.

triangle square 5

Step 6:

Now you can turn the unit back over to the right side and press as shown below. Half done!

newsletter sign up

triangle square 6

Step 7:

Repeat Steps 3 through 5 for the opposite diagonal seam.

triangle square 7

Step 8:

Once again, fold back the template paper on the seam line and trim the seam allowance as shown in the picture below.

triangle square 8

Step 9:

Turn back over and press as shown in the picture below.

triangle square 9

Step 10:

With the template side facing up, trim the unit along the dotted lines to make a 4.5" square as shown below.

triangle square 10

Step 11:

Remove the template pieces. You will probably need to finger (fingernail) press on the seam lines to get the paper to tear easily.

triangle square 11

Step 12:

Here's a picture of the completed block.

triangle square 12


I tried out two different rulers that are made for constructing this block. First we'll look at Quilt in a Day's Triangle in a Square Rulers by Eleanor Burns.

quilt in a day ruler

The rulers I purchased can make 3" or 4" units. The instructions that come with the rulers are very good with lots of illustrations. However, on my copy, the coloring was wrong on the 5" strips for the 4" unit - it was correct the rest of the way through the instructions. There is also a pattern included!

Eleanor has you cut 6" strips to make the side triangle pieces and 5" strips to make the center triangle pieces. At the end, you will trim up the unit to get the correct size. 

Here you can see my finished block:

ruler 1 finished block

The second ruler I tried was the Tri Recs Triangle Rulers designed by Darlene Zimmerman and Joy Hoffman with EZ Quilting.

tri recs ruler

The Tri Recs rulers have markings to make from 1" to 6" finished units which is nice to have all those sizes in one set of rulers. The instructions included with the rulers are okay but you'll need your reading glasses to read them!

Darlene and Joy have you cut strips to the same width as your unfinished block - in my case 4.5" wide. So there was little waste but also little room for error. 

Here's my finished block. The bottom corners are off a little but that shouldn't make any difference once they are sewn into a block. I thought I lined everything up right, but maybe not. Also the top edge of the block isn't quite 4.5" (I probably took slightly more than 1/4" seam at the top).

ruler 2 block


While the Triangle in a Square isn't the hardest block to make, the paper piecing part was probably the hardest tutorial for me to make. I'm not a super paper piecer but I love the results you can get with paper piecing. I highly recommend the book "Paper Piecing with Alex Anderson" for in depth, how-to instructions (and 6 projects!). 

While the way I paper pieced this block had the most waste, I got the best results with it. You could cut oversized triangles for the center triangle instead of using a square and the cut off part of the Dark/Purple side triangles could be used for another unit. Those two things would reduce the waste by quite a bit.

The Tri Recs rulers used the least amount of fabric but my results weren't the best. I would need to practice with it more to get good results.

hope you've enjoyed this Triangle in a Square quilt block. If you liked this post and want to see more quilting tutorials like this, simply click here to sign up for my newsletter and also receive a free PDF quilt pattern called Chained Weathervane.

Happy Quilting!


P.S. To print a PDF of this tutorial, check out the free app at

P.P.S. To figure out yardage for a quilt, check out this post:


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