When you need lots of identical half square triangles (HST) and want them fast, make eight at a time! With this easy and quick method, you can mass produce blocks, but the outside edges are all on stable straight-of-grain – no bias edges! So if you have a quilt pattern with lots of matching half square triangles, this technique is perfect.
Half Square Triangles Eight at a Time Block Calculator
With some easy math, you can make any size HSTs for your next project! Just use this formula. (See common sizes listed below for quick reference.)
To calculate any size HST: Start with your finished block size and add 7/8″, then multiply by two. (Finished block size + 7/8″) x 2 = size to cut fabric squares. Cut two contrasting squares for each set of eight (8) half square triangles.
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- 2″ finished block: (2 + 7/8) x 2 = 5-3/4. Cut two squares at 5-3/4″ to make eight (8) 2″ finished half square triangle blocks.
- 3″ finished block: (3 + 7/8) x 2 = 7-3/4. Cut two squares at 7-3/4″ to make eight (8) 3″ finished half square triangle blocks.
- 4″ finished block: (4 + 7/8) x 2 = 9-3/4. Cut two squares at 9-3/4″ to make eight (8) 4″ finished half square triangle blocks.
- 5″ finished block: (5 + 7/8) x 2 = 11-3/4. Cut two squares at 11-3/4″ to make eight (8) 5″ finished half square triangle blocks.
- 6″ finished block: (6 + 7/8) x 2 = 13-3/4. Cut two squares at 13-3/4″ to make eight (8) 6″ finished half square triangle blocks.
- And, so on.
Here is an alternate layout idea for using the half square triangles:
Some of our favorite quilt blocks that use half square triangles:
Browse through more quilting inspiration and projects on Create Whimsy.
Check out various ways to make half square triangles.