The Ultimate Guide To Sewing Half Square Triangles

The half square triangle, abbreviated to HST in most quilt patterns, can be found in so many different blocks such as the Road to Oklahoma block, the Whirlpool block and the Star Puzzle block.

Sample Blocks   

                                                                                 Road To Oklahoma Block

Whirlpool Block

                                                                               Star Puzzle Block

In this blog post we are going to look at making the humble HST using three different methods. You will find a photo tutorial, a YouTube video tutorial which includes how to trim the HST's, and a cheat sheet to help with the measurements.

Half square triangles can be made by stitching two right angled triangles together, for example one print and one plain, but this method means you will be sewing two bias edges together which can stretch very easily when sewing, and is a slow way of making them. A much more efficient way is to make them 2, 4, or 8 at a time! 

Supplies needed

• FABRIC - Quilting fabric or tightly woven cotton fabric, two different colours, prints or one of each.
• CUTTING TOOLS - Rotary cutter and a cutting mat. If you have a rotating cutting mat it makes it really easy to trim HSTs.
• RULER - Quilting ruler, a square ruler would be ideal, your ruler will need 45 degree lines etched on it.
• MARKING TOOL - A fabric marker, either washable or disappearing. I use a Pilot Frixion pen which disappears with heat. I only use it where the pen marks won't be seen as it has been known to leave a white mark on some fabrics, even after washing.
• PINS OR CLIPS - to hold fabrics together
• SEWING MACHINE
• THREAD - either matching thread or a neutral colour. I use Gutermann 100% polyester for piecing in colour 38, which is a mid grey, I find this colour blends in with most fabrics.
• PRESSING MAT AND IRON - or an ironing board and iron.
• SEWING SCISSORS
• SEAM ROLLER - optional. I use a seam roller to initially press my HST open before pressing with the iron before sewing.

Half Square Triangle Cheat Sheet

Use this guide to decide what size to cut the squares. Do you want a printed copy to keep? Click the link or guide to send to your printer!

Half Square Triangle Tutorial

Use this photo tutorial along with the YouTube video to stitch a bundle of HSTs! Click the link or guide to send to your printer!

Pressing your HSTs open is a skill in itself! Press the seam of your unopened HST to set it before proceeding. The idea is not to iron them as if you were ironing your clothes, but to just press the iron down on the square, then lift and move to another part of the square and press. I press my seams to one side, mostly to the darker fabric, but sometimes depending on how the pattern is constructed I will press to the lighter side. I very occasionally press the seam open, especially if there is going to be a lot of bulk. With the seams pressed to one side it is easier to nest them with other seams when sewing the rows together. I have noticed that some quilters use steam to press their seams, I don't, but this is a personal preference.

Video Tutorial For Half Square Triangles

I hope you enjoy creating with Half Square Triangles, I would love to see your projects!

Happy Sewing!