Half Square Triangle Calculator

Do you find yourself dreading quilt math? Well dread no more with this Half Square Triangle calculator! Simply plug in the size you want your HSTs to finish at, and the calculator will do the math for you! Once you type in your finished HST size, use the measurements on the right. They’ll indicate which size squares you need to cut to create the HSTs you want. You’ll get measurements for 2-at-a-time, 4-at-a-time, and 8-at-a-time methods. The calculator gives you measurements in inches.

For 4-at-a-time Half Square Triangles, round the number up to the nearest 1/4″. For example, if the calculator tells you to cut 9.375″ squares, round up to 9.5″ and cut two squares that size to make your HSTs.

FYI! Finished size means the size once it is all sewn into your project. Unfinished size is the size you trim to when creating your HSTs. You’ll use the finished size in your measurements below, but remember to trim HSTs 0.5″ bigger!

Two columns
Half Square Triangle Calculator
Size Squares to Cut:
Name Total
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Having trouble with the Half Square Triangle Calculator? Try it on desktop!

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half square triangle calculator

Additional Half Square Triangle Resources:

If you’re new to making Half Square Triangles, I have a handy printable guide with step-by-step diagrams for all three methods! If you’re looking for help trimming, I’ve got two separate videos to help with that too!

half square triangle quick start guide

Half Square Triangle Guide

Includes step-by-step tutorial for 2-at-a-time, 4-at-a-time, and 8-at-a-time half square triangles & printable cheat sheet!
Read the blog post

6 thoughts on “Half Square Triangle Calculator

  1. Thank you! I used it to confirm my calculations for setting triangles that have to be cut 2 from one block. Yes, I know, there will be bias edges but I am going to fuse a sheer weight interfacing strip on the diagonal before I cut.

  2. Hi Eliane, thanks so much for the quilting calculators, genius!! They will be so handy! I also want to thank you for sharing your talent and creativity with the world. I wish you much success in your business!

  3. This is fantastic! You have a place where you say “Try it on desktop!”
    Does that mean we can somehow do this from the desktop of our computer?

  4. I’m planning to make a large Double Carpenters’ Star in 3 colours. Your calculator is a great tool. Thank you.

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