A half square triangle is one of the most basic (and easy!) quilting pieces.

Once you master these, you'll be able to use them in lots of different quilt blocks. They can be arranged to make a multitude of patterns.

There are a few different ways to create a half square triangle (HST). You can make 4 at a time, or 8 at a time.

But today, we're going to focus on the simplest method for cutting and sewing half square triangles.

HALF SQUARE TRIANGLES

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image of two half square triangle quilting piece with the words simple half square triangle tutorial

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This year, I am focusing on the art of piece quilting. I am going to be making quilt blocks that were used during the time of the Underground Railroad. I'll be sharing the blocks as I go as well as the smaller units that make up the block, like these half square triangles.

Check out more Easy Quilt Blocks for Beginners, and Quilting Rulers Every Quilter Needs

The first block I'm making is called Jacob's Ladder and it uses both half square triangles and four patches to make up the block.

To find lots of patterns utilizing the HST's check out 40+ Half Square Triangle Quilts.

This post may contain affiliate links. Please see my full disclosure policy for details.

SUPPLIES NEEDED FOR HALF SQUARE TRIANGLES

fabric
thread
rotary cutter / cutting mat / straight edge
sewing machine
sewing scissors
pencil
iron and ironing board
4 1/2" square quilting ruler

HOW TO MAKE A HALF SQUARE TRIANGLE

Gather your supplies and let's get started.

Begin with two pieces of fabric that are five inches square. Once they are added to the 12 inch block their final size will be 4 inches square.

Need a different size?

Try this formula for half square triangles:

Begin with two fabric squares that are equal to the size of the finished square plus 7/8 inch.
The additional 7/8" is for the seam allowance. (I like to add a full inch extra and square it up after the fact - that allows for a little wiggle room)

fabric squares with right sides together

With right sides together, place one fabric piece on top of the other.

tracing a line from corner to corner of square fabric

Place a ruler from one corner to the opposite corner. Draw a line along the straight edge.

On both sides of the pencil line, sew a seam 1/4 inch from line.

Cut along the pencil line. Open the half square triangles. You will now have two squares, each half of a different color. Press the seam towards the side of the square that has the darker colored fabric.