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How to turn an octagon into a square

April 27, 2018 6 Comments

I started this quilt a few years ago (pattern here) and I am happy that  I am finishing it (my baby nephew needs a new quilt!).
It started with a 2” octagon; 8 triangles surround it. The result is a new octagon.

Other triangles were added and a new octagon was born.

One more time! Isn’t the Fossil Fern fabric (by Benartex) gorgeous?

A new octagon! I love this shape but it was too small for what I need so I decided to add borders. But first, I had to turn the octagon into a square. This is an easy task- you just have to add corner  triangles.

Figuring out the size of the triangles is easy as well. I thought to take pictures and share this with you, in case you need some guidance.

First, you have to place the block onto a cutting mat (or square ruler), aligning the top and right edges with the starting lines of the cutting mat (see the red arrows), as shown below. We have to determine the size of that red triangle marked below.

Measure the small sides of the red corner triangle (see below); they should be equal. Add 1½” to that measurement and cut 2 squares of that size, in the color you want for your borders. Cut the squares diagonally; you will end up with 4 half-square triangles and you will add them in 4 corners of the big octagon.

Here is one of the triangles.

Center the triangle over the corner, stitch with 1/4” seam allowance and press.
The triangle is oversized so it needs some trimming.

Use a big square ruler (I LOVE my 20” square ruler!) and align the top and right edges of the ruler with the top and right edges of the octagon (see the red arrows).

Trim off the excess fabric.  Repeat for all the corners.

The octagon turned now into a square should look like this.

Then I added the borders and I noticed that I did not follow my own advice: the fabric outside the octagon (the corner triangles and borders) should contrast well with the fabrics of the octagon. Fortunately, I don’t think that the baby boy (11 months!!) who will receive it will ever complain about it!

But I still wanted to try to fix this mistake, so I thought to quilt the octagon and the space outside the octagon differently, hoping that the difference will make the octagon design more apparent!

So here is how I quilted  the octagon: a vertical grid…

Then a horizontal grid…

Then concentric octagons outside the big octagon design…

This is the look… not very happy with it…

…so I thought to add even more stitching outside the octagon. And here is the result…acceptable!

This one would have been better, right? Thank you, Photoshop!

Happy sewing!


Interested to learn the technique used to sew this modern geometric design?

 

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Filed Under: finished quilts, quilting tutorials Tagged With: quilt, quilt tutorial

Comments

  1. Kelly Bunnell says

    April 27, 2018 at 1:11 pm

    This is really cute!!! Thanks for sharing your oops and also sharing how you fixed it. Sometimes our oops turn out to be a good thing. I really needed an easy way to add triangles to make a square. Thanks again for sharing this information.
    Kelly

    Reply
  2. Susan says

    April 27, 2018 at 1:17 pm

    Thank you for this tutorial. No quilt math involved!

    It is amazing how much bigger they get each time. What size octagon did you start with in the center for this block?

    Reply
    • Geta Grama says

      April 28, 2018 at 9:45 am

      Susan, the center octagon measures 2”; the final block is about 28”. The size of the triangles increases exponentially.

      Reply
  3. Martha says

    April 27, 2018 at 5:23 pm

    With border matching some of the inner portion, this octogon-to-square could be a pattern called “Whirlygig”. 🙂 Thanks for these steps to create the right size for triangle corners.

    Reply
    • Geta Grama says

      April 28, 2018 at 9:46 am

      Yes, you’re right, Martha.

      Reply
  4. Mary >^..^ says

    April 28, 2018 at 1:30 am

    My favorite shape is octagon.
    My favorite fabric is fossil fern.
    I love the colors.
    We must be sisters.

    Reply

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