How to Sew with Isosceles Triangles

Over a year ago, I was at Jo Ann’s Fabrics looking to buy a triangle ruler. I loved all the triangle quilts showing up all over Pinterest. As I was browsing at Jo Ann’s, I asked one of the employees if she had any tips for sewing triangles. She had some not so kind words to say about triangles, and then she kind of just went on with her work.

After a few attempts at sewing with isosceles triangles, I understand where she was coming from.

I started sewing a twin size triangle quilt a month ago. I have almost burned it. Twice. It has caused a bit of friction in our marriage. Because, see, I am married to an engineer. How can he graduate college without understanding the geometry behind sewing a quarter of an inch seam allowance down the side of an isosceles triangle?

I have read all the instructions about sewing with triangles. You have to stagger your triangles by a quarter of an inch.

Please understand I am far from being a perfectionistic sewer, but I couldn’t bear to look at my points on this one.

Solution: I stopped sewing the twin quilt and figured out how to take the guessing game out of sewing with triangles.

If this is your first time attempting to sew with triangles, I recommend starting with something small. I sewed a burp cloth with these triangles.

How to Sew with Isosceles Trianges. Tips for a triange quilt.

1. Cut your fabric into 4 1/2 inch strips. I used one strip of three colors. The strips were the length of the width of the fabric. I used Kona white, Kona snow, and Kona dusty peach.

How to sew a triangle quilt. Sewing with isosceles triangles.
2. Using a triangle ruler, cut your strips of fabric into triangles. Line it up with the bottom of the fabric. Be sure the left side lines up well, or you may want to do some trimming if everything isn’t lining up well. The more precise you are when you cut your triangles, the easier it will be to get your points sharp!

How to sew a triangle quilt. Sewing with isosceles triangles.
3. Line up a ruler with the bottom of the triangle, and make a mark an eighth of an inch from the bottom. I was finally able to get my triangles to line up well when I started marking them. Once you have sewn enough triangles, you will start to get the hang of it. If you end up with a triangle that doesn’t line up, you’ll begin to understand why after sewing quite a few.Β  (Pardon my husband’s ruler from elementary school.Β  It used to be cool to write your name on everything with white-out.)

How to sew a triangle quilt. Sewing with isosceles triangles. How to sew a triangle quilt. Sewing with isosceles triangles.
4. Using the mark as a guide, line up the blunt tip of one triangle with the mark of another triangle.

How to sew a triangle quilt. Sewing with isosceles triangles.How to sew a triangle quilt. Sewing with isosceles triangles.
5. Sew a quarter of an inch down the sides of the triangles. I learned that a scant quarter of an inch works best. Don’t overshoot a quarter of an inch seam allowance.

How to sew a triangle quilt. Sewing with isosceles triangles.
6. Iron the seam open.

Sewing with isosceles triangles. How to sew a triangle quilt.
7. Repeat the process above. Take another triangle and line up the blunt end with the mark an eighth of an inch from the bottom of another triangle.

How to sew a triangle quilt. Sewing with isosceles triangles.How to sew a triangle quilt. Sewing with isosceles triangles.
Sew another scant quarter of an inch between the two triangles. Pretty soon you will have nice, neat, and straight rows of triangles.

How to sew a triangle quilt. Sewing with isosceles triangles.
8. Pin the rows together. I recommend putting the pin straight through the points of the triangles so you know exactly where the points are.

How to sew a triangle quilt. How to sew a triangle quilt.
9. Sew the rows together. SHARP POINTS! Sew right through the intersection of the points. In other words, sew right through where you stuck your pin through.

How to sew a triangle quilt.
After I finished sewing four rows of triangles, I used them to make the most adorable burp cloths for two new moms at church. I used some extraordinarily plush terry cloth that I will buy again and again for gifts.

I was reading the reviews on it because I wasn’t sure I wanted to pay $16.98 a yard. I decided to try it since the reviews were so good, and since I was purchasing it for a gift, I felt splurging was a bit more acceptable.

This terry cloth really was super thick and soft. I would likely not buy this same terry cloth to make home made napkins or a drying mat because I don’t need something that high quality. For a gift, I felt the expensive terry cloth was worth it.

the most absorbent terry cloth, thick terry cloth

Home made absorbent burp cloths
Kona Cotton Dusty Peach
/ Kona Cotton White / Kona Cotton Snow

Homemade Burp Cloths: A Simple Gift for a New Mom
Don’t hesitate to ask questions in the comments. Or LEAVE SOME TIPS if you have some great ones for sewing triangles.

Here is the triangle quilt I referenced above. It was a rather frustrating process as I learned the art of sewing with isosceles triangles. But, I kept trying and kept learning, and I have figured out what works best for me.

How to sew with Isosceles Triangles

(Please note that there are affiliate links in this post.)

10 thoughts on “How to Sew with Isosceles Triangles

  1. Thank goodness I found you! I had no idea this would be so hard!! I consider myself an experienced seamstress and I simply could not figure it out. Dang it! So thank you very much. I love how you quilted it also.

    1. Hi Robyn, I’m thankful this was helpful for you! Sewing an isosceles triangle quilt was probably the most frustrating quilt I ever tried. But I’m glad I finished. πŸ™‚ I hope you are enjoying the process!

  2. Thanks for the awesome tutorial. Have tried these triangles twice and was reduced to tears following the older instructions. Tried your method and there is definitely going to be a triangular quilt being made in the near future.

    1. Karen, I have shed some tears over triangles too. They were so frustrating for me! Just remember, stagger them by an 1/8 of an inch and sew a scant quarter inch between rows. That seemed to solve almost all my triangle problems.

      I am SO THANKFUL to hear this method is working for you! And THANK YOU for leaving me a comment. I am always so encouraged when someone found this tutorial useful.

      Good luck and if you end up with a quilt, please send me a picture. πŸ™‚

    1. Hi Susan! I’m glad they inspire you! It took a bit of trial and error for me to figure out what worked best for me, but I’m thankful I kept ripping out seams until I figured it out! πŸ™‚

    1. Hi LynnAnn, if you are anything like me, you should try! But don’t get too frustrated too fast if they aren’t perfect. Learning to sew with isosceles triangles took me a few tries, but it’s been worth it!!

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