How to Sew a Triangle Quilt

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Triangles, triangles, triangles.

They’re a lovely shape for sewing one block quilts. I’ve loved triangle quilts since I first started seeing them in my early years of sewing.

Sewing a triangle quilt was actually one of my very first quilt projects. It was an extremely frustrating project. I hadn’t done any research at all. I ran across a quilt that inspired me to make a triangle quilt. I went to Jo-Ann’s and bought a triangle ruler. I went home and started sewing.

A couple weeks later I remember sitting at my parents house asking my mom to help me rip the seams out of my quilt top.

Nothing was lining up. The seams were a mess. And the points were definitely not sharp points.

I attempted a few other triangle projects in my early years of sewing, and they were always just a bit off.

I’m here today to tell you that with a bit of experience, growth in precision, and investing time in a hobby, things do get easier.

These triangles came together fluently and joyfully. They’re not all perfect, and I’m not a perfectionist quilter.

Triangle quilts can be sewn, my friends.

Before I show you a few step by steps, let me offer a few tips. These are tips regarding isosceles triangles. I believe everything is a bit different if you’re sewing equilateral triangles (where the sides are the same length on all three sides.)

1. Don’t just jump in like I did. You must learn to stagger your triangles as you go.

2. These tips are only helpful if you have a triangle ruler with a blunt tip.

3. I haven’t figured out the best way to iron the seams for triangles. For me, it worked best to iron after every seam. In other words, sew two triangles together and iron. Add another triangle and iron. Add another triangle and iron.

4. Nesting my seams made everything better. It prevented the bulk at the points of the triangles.

5. My sewing machine is a middle of the road sewing machine. It has trouble sewing through the bulk where where the triangles meet. Using a walking foot helped at times.

Where are my favorite places to browse for new fabrics?

Modern Violet – great small shop for fun Heather Ross prints.
Fresh Modern Fabrics – large variety of fabrics with many prints.
Morgan Kelly Quilts – a great place for fabric bundles. Since she doesn’t carry a high selection of fabric, it’s a good shop to browse if you’re overwhelmed easily.
Sew Organic – excellent experience with customer service & all organic fabrics.
Field and Cloth – perfectly curated selection of rich and textured fabrics.
Kiwi Fabric – wide variety of many fabrics. Fast shipping.
Fabric.com – great when buying multiple yards for backing.
Polka Dot Secrets – lots of florals and real pictures of the fabrics.

How to sew an isosceles triangle quilt:

1. Find a triangle ruler with a blunt tip (like in the above picture.) The triangle ruler I have pictured above is not sold anymore. This is a 45 degree angle with a blunt tip. I found two options online that I believe will work just like this one.

Fat Quarter Shop
Modern Quilter on Etsy

2. Cut your triangles. I cut six inch strips of fabric. There are marks on your triangle ruler to line up with depending on how wide you cut your strips.

3. Begin sewing your triangles together. This is where things can get tricky.

Choose your two triangles. Lay them side by side like the above picture. Turn the blue triangle over on top of the yellow triangle.

You must STAGGER YOUR TRIANGLES.

Use the blunt tip as your guide. See in the above picture how I staggered the triangle so that the blunt tip fit perfectly between the edges of the yellow fabric. This is so very important since it’s what will create a quarter inch seam along the top of your triangles.

Below is another picture of the two triangles ready to sew together.

4. Sew a precise quarter of an inch seam to join your triangles. If you aren’t sure you are sewing a true quarter inch seam, double check yourself. It will make your life exceedingly easier.

See this post for details about sewing a quarter of an inch seam allowance.

5. Iron the seam. I’m not sure I’ve found the BEST way to iron the seams.

I learned that ironing after every triangle worked best for me. In other words, I can’t chain piece triangles. I sewed two together and then ironed. I added another triangle and then ironed. I added another triangle and then ironed.

I also learned to press one row all to one side and press the next row to the other. This created seams for nesting. If I didn’t nest them well, I ended up with huge bulk at the points.

6. Add another triangle.

Once again, use the blunt end as a guide and sew a quarter of an inch seam.

Here’s my three triangles together. You can now see below the blue triangle how we’re creating a seam allowance for sewing the rows of triangles together.

7. Iron the seams of one row all one direction. See below what the backside of my triangles look like.

8. Finishing sewing your row of triangles.

I sewed nine together. This will work well for an 18 inch square pillow cover when I’m done. If you’re sewing a quilt, obviously you’d need a LOT more triangles.

9. Sew another row of triangles. Be sure to press the seams the opposite way.

10. Trim off the excess fabric above the tips. This step may not be necessary depending on your sewing machine foot.

For me, that little tip gets in the way of my sewing. It’s worth the time and effort for me to clip them all off.

Below is simply what it looks like after clipping the tip off.

11. Lay your rows right sides together. Nest your seams as best as you can, and sew your two rows together.

12. Continue sewing rows until your quilt top or pillow top is done!

And if this is your first time sewing triangles, don’t judge your pointy tips…or lack thereof.

Look closely below. The two points on the right are perfect. The two points on the left are not perfect. It’s part of the creative process, friends, and I can testify that quilting is MUCH more enjoyable when you aren’t bothered by the small imperfections.

Check back soon for pictures of finished triangle pillows!