Basic machine-piecing: Half-square triangle units

Half-square triangle unit

“Half-square triangles” are a standard small unit which occurs frequently in patchwork.

Instead of cutting out two triangles, it is quicker and more accurate to make two at a time from squares, using a “quick-piecing” technique. Look at the video below to see how this is done.

Many different blocks can be made either just using these useful little units, or by combining them with squares:

Windblown Square
Windblown Square block made entirely with half-square triangle units
Yankee Puzzle Block
Squares and half-square triangles combined into Jacob's Ladder block
Jacob’s Ladder block
Double Cat block



Why not try this technique out by making a Double Cat block – click here for a free download pattern

There are plenty of projects which include half-square triangles.

Have a look at the Wall hangings page or in my Shop

Calculating sizes for your own projects

It is easy to calculate the size of squares that you need to cut.

Simply add 7/8″ to the finished size required. This works with all sizes!

e.g. to make two half square triangles that will make a four inch unit when stitched into a block, cut a square of each colour which measures 4 7/8″, and quick-piece as shown in the video.

Pieced Borders

Half square triangle units are also useful for pieced borders, either on a single block like this, or around a quilt or wallhanging:

Half-square triangle units combined into a block
Formal Garden block in a twisted setting with two pieced borders

If you would like to try making a small project which includes a pieced border, the download pattern for the Catherine Wheel project shown here is available in my Shop for £8.
Full instructions for making the pieced border fit perfectly are included.

Catherine Wheel
Catherine Wheel – a small wall hanging

On a larger scale, half square triangles are also used for the inner border of this Solitaire bed quilt:

Large bed patchwork quilt in pink & purple

For other tips and guidance, look at the Machine-stitched patchwork page

Choose a project from my Shop – all patterns can be downloaded at a cost of £8, and include plenty of details to help you get really good results.