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HOW TO MAKE HALF SQUARE TRIANGLES – Simple Half Square Triangles

HOW TO MAKE HALF SQUARE TRIANGLES – Simple Half Square Triangles

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So you’re new to quilting and you wonder How Do You Make Half Square Triangles?  I’m here to show you the most outrageously EASY and simple way to cut and sew a half square triangle block.  Half Square Triangles are seriously one of the most versatile blocks to sew and hands down are my favorite.


They are simple, look good in nearly any fabric choices, and can be used to make countless combinations.  


If you don’t want to think about the math, you can find my Half Square Triangle-based quilt – The Maid Modern Quilt in the shop. It is a minimal modern design that comes in baby and throw sizes.

I have several Half Square Triangle Quilts that are currently in the works (you can see the mini quilt patterns here and here), so I decided to do a simple Half Square Triangles Tutorial so you can make some too! There are several different ways to make half square triangles, each having their own pros and cons, so I am going to be doing a series on them this month covering all the different ways to piece HST’s, some quick HST math cheat sheets, the different patterns that can be made using HST’s, and what type of piecing method is best for what type of project.

First, you might ask, What is a half square triangle?

  • A half square triangle is a basic quilting block.
  • It is when you make a whole square quilt block from two half square triangles.
  • The half square triangles will need to have both sides be the same length and the triangles must be the same size as each other to form a square.
  • Often the name of these blocks will be shortened to HST in the instructions of the pattern.
  • Depending on how the half square triangle is cut, the bias edge (diagonal grain of the fabric) will be either enclosed in the seam or on the outside edges of the square.
  • In this tutorial, the bias seam is enclosed in the diagonal seam, which makes it less likely to distort when handling and pressing it.  This is the preferred beginner method.

Ways to Make Half Square Triangles

This is the first installment of the Half Square Triangle Series.  You can see all of the Half Square Triangle Series below:

  1. Method I – Making Half Square Triangles Tutorial – Simple Half Square Triangles
  2. Method II – HST Tutorial 4 at a Time
  3. Method III – The Magic 8 Method – Make 8 HST at Once
  4. Method IV – Make Half Square Triangles from a Jelly Roll – The Strip Method
  5. Method V – How to Use Half Square Triangle Paper
  6. 25+ Half Square Triangle Quilt Patterns


This is the original tutorial that was made several years ago. The graphics are simple and easy to understand. I have updated the post with new pictures and a video including some great tips for more accurate Half Square Triangles. I am leaving the original here, but you can scroll down to find the photo tutorial and new tips.

  1. To make a Half Square Triangles (HST) place two equal-size square Right Sides Together (RST).  Mark a diagonal line on the wrong side of the top fabric square.  
  2. Place the squares RST with the marked square on the top.  Stitch 1/4in on both sides of the marked line.  

3. Cut down the marked line to make two new squares.  

4. Open the half square triangle blocks outward. 


5.  Press seam (both layers) toward the darker color. 

6.  Place a ruler on the block keeping the 45-degree diagonal line over the diagonal seam.  Trim to your square to the desired size.  There will now be two Half Square Triangles (HSTs).



Supplies Needed:

This tutorial is essentially the same as the graphic one above but completed in photo steps for those who prefer this method.

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Etta Combs

Sunday 17th of May 2020

I am reverse engineering a quilt. I am trying to determine the definition of the finished square. Is it the size ie 2.5 with the seam allowance left on til added to the quilt or is it the finished size once sewn in place, ie 2.0 inch? I am leaning to the 2.5 because the block would still need to be added to the rest of the pattern. Can you please confirm? I look forward to making 8 HST at a time! I am making 2 Baby Thunderbird quilts and need 64 HST for wings.


Thursday 28th of May 2020

Finished would be before you sew it to another square. It is once the triangles are joined and trimmed.


Thursday 7th of May 2020

So you absolutely cannot use Charm Squares to do Half square triangles. No wonder I had such a problem. Thank you.

Carol Casperson

Thursday 27th of February 2020

Love your site and info. Great help to us beginners


Thursday 27th of February 2020

Thank you so much!


Sunday 4th of March 2018

Thank you!!!!!!

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