Friday, April 20, 2012

30 - Equilateral Triangles

Tutorial for a 12 inch Equilateral Triangle Block
Ahhh...I enjoyed making this block much more than the apple core block.  Triangle quilts have been popping up all over blogland recently.  In fact there is even a Patchwork Prism QAL starting up that uses equilateral triangles -- I may just have to join in.

triangle quilt
An equilateral triangle quilt, by Constança Cabral via flickr
Before we get to the block, let's review some basic geometry.  A triangle has three sides.  So far so good.  ;)  An equilateral triangle has three equal sides and three equal angles.  All of the angles on a triangle add up to 180 degrees.  Since each of the three triangles on an equilateral triangle are equal, the corner angle can be determined by dividing 180 by 3.  180/3=60  Each angle in a equilateral triangle is 60 degrees.

20120409 Triangle Quilt-3
An example of an isosceles triangle quilt by Audrie of Blue is Bleu via flickr
An isosceles triangle has two sides and two angles that are the same.  The third side can be either shorter than the other two (like the quilt above) or wider like a half square triangle.  A half square triangle is both a right triangle and an isosceles triangle, for those who want to go the extra geometric mile.  Check out this site for more fun triangle facts.

The first step to make this block is to make a template.   You can cut the triangles without a template, but it involves a lot of thinking and moving your ruler around to find the right angle.  A template is much easier.

Cut a piece of paper or card stock 3.75 inches tall.  The quilt math rule for equilateral triangles is that the unfinished triangle needs to be cut 3/4 inch taller than the desired finished size.   Our finished triangles will be 3 inches tall.

Next identify the 60 degree marking lines on your ruler.  Also remember that the other side of the 30 degree line is 60 degrees.  How do we know that?  The ruler has 90 degree angles in each corners.  90 degrees minus 30 degrees equals 60 degrees.  Still doesn't make any sense?  Just trust me and know that you might have to use your 30 degree angle to make the template.

Cut one side of the template off at a 60 degree angle (you might have to line it up with the opposite side of the 30 degree mark for the ruler to be long enough to make the cut).  Next line up the 60 degree line with the cut angle and make a second cut.  This is the template.

I find it easiest to use the template when it is attached to the back of the ruler.  Tape the template to the back of your ruler with one of the sides along the edge.

Cut a strip of fabric 3.75 inches wide.  Line up the bottom of the template with the bottom of the strip of fabric with the ruler edge facing the end of the fabric strip.  Cut.

Turn the ruler and line up the bottom and left edge of the template with the bottom and left edge of the fabric.  Cut.  Continue cutting all the way down the strip of fabric.  Cut a total of 32 triangles.  I cut 16 white triangles and 16 blue triangles out of various fabrics.

Arrange the triangles as desired in four rows of eight triangles.


Sew each row together.  Place the first two triangles in the row right sides together and sew down the side with a 1/4 inch seam.

Next open up the triangle and lay the next triangle next to it.  Flip the third triangle on top of the other two.

Line up the corners of the triangles and make sure the seam is off to the side.  Sew with a 1/4 inch seam.

Keep adding triangles until you have sewn all six together.  Repeat for each row.

Press seams very carefully to the side.  The sides of the triangles are cut on the bias and will stretch very easily.  However, this can work in our favor.  If your rows are slightly bowed give the row the tiniest of pulls as you press to straighten it.

Use a ruler and rotary cutter to cut off the dog ears.

 Sew the four rows together pinning at the seam intersections.  Then trim the sides of the block so that the block is 12.5 inches wide.

You did it!  
How did you like it?  Have you made a triangle quilt before?


  1. Great pictures and tutorial! I ahve never made a triangle quilt (except HSTs...) but I really want to!

  2. After the apple core this looks nice and easy :)

  3. Great tute!! Thanks! I have done LOADS of triangles, so this one will be really fun!! Yea!

  4. This does look simpler, and more relaxing. So what can go wrong? Hmm.

  5. Leila--that opening photo of those triangles is just deliciously perfect! You've got some amazing piecing skills, I'd say. Love the blue and whites, and the other triangle quilts look terrific, too. Great post!

  6. This is a great tutorial, thank you for sharing! Fi

  7. I've wanted to make one of these for a while now! Great idea taping it to the ruler, that made it so much faster!! It was easier than I expected and so fun! I will seriously be making one of these again!

  8. wonderful work!! so, you have excellent experience for creating Prism quilt! :) and I will do it first time!! oh.... :)
    thank you for comment on my Flickr photo!
    hugs from Russia,

  9. Amazing work , congratulatios from Brazil .

  10. I don't understand "seam is off to the side." I'm really having trouble with these things!

  11. I've never seen the "tape the template to the ruler" tip before...I will try that. Thanks :)

  12. head is spinning...if I would have known in high school that I would later love sewing I would have really paid more attention in Math/Geometry! Thankfully you have excellent pics, but I don't think I am ready for this level yet, will save for future:)!

  13. Great tutorial! Thank you so much! I cannot wait to try this.

  14. What a great tip taping a template to the ruler, thanks so much!