Half square triangles
Half Square Triangle Size Chart: Cut Sizes by Method
For two-at-a-time half square triangles, cut squares 7/8 inch larger than the finished size, or 1 inch larger to trim. Four at a time uses squares about 1.41 times the finished size plus 1 1/4 inches, and eight at a time uses squares twice the finished size plus 1 3/4 inches. A 3 inch HST uses 3 7/8 inch squares.
| Finished | Unfinished | 2 at a time | 2 at a time, trim | 4 at a time | 8 at a time |
|---|---|---|---|---|---|
| 1 1/2 in | 2 | 2 3/8 | 2 1/2 | 3 3/8 | 4 3/4 |
| 2 in | 2 1/2 | 2 7/8 | 3 | 4 1/8 | 5 3/4 |
| 2 1/2 in | 3 | 3 3/8 | 3 1/2 | 4 7/8 | 6 3/4 |
| 3 in | 3 1/2 | 3 7/8 | 4 | 5 1/2 | 7 3/4 |
| 3 1/2 in | 4 | 4 3/8 | 4 1/2 | 6 1/4 | 8 3/4 |
| 4 in | 4 1/2 | 4 7/8 | 5 | 7 | 9 3/4 |
| 4 1/2 in | 5 | 5 3/8 | 5 1/2 | 7 5/8 | 10 3/4 |
| 5 in | 5 1/2 | 5 7/8 | 6 | 8 3/8 | 11 3/4 |
| 6 in | 6 1/2 | 6 7/8 | 7 | 9 3/4 | 13 3/4 |
| 8 in | 8 1/2 | 8 7/8 | 9 | 12 5/8 | 17 3/4 |
The chart above gives the cut size for every method at 10 finished sizes: a 3 inch HST is cut from 3 7/8 inch squares two at a time and squares up to 3 1/2 inches before it is sewn into a block.
For any other size, use the half square triangle calculator, and see how to make half square triangles for the sewing order. Multiply a finished HST by the units across a block to find the quilt block size it builds, or turn the same grid into flying geese for star blocks.
Frequently asked questions
What is a half square triangle?
A half square triangle, or HST, is a square unit made of two right triangles sewn together along the diagonal. It is the most common pieced unit in quilting, and it builds pinwheels, sawtooth stars, bear paws and chevrons. An HST that finishes at 3 inches is cut from two 3 7/8 inch squares and measures 3 1/2 inches before it goes into a block.
What size square do I cut for half square triangles?
For the two-at-a-time method, cut squares 7/8 inch larger than the finished size, so a 3 inch HST needs 3 7/8 inch squares. Cutting a full inch larger and trimming back is more forgiving of a slightly wide seam. The chart on this page lists the exact and trim-to sizes for every finished size from 1 1/2 to 8 inches.
Which half square triangle method is fastest?
The magic eight method is the fastest per unit, because one pair of squares yields eight HSTs instead of two. A 3 inch HST needs 7 3/4 inch squares for eight at a time, against 3 7/8 inch squares for two at a time. Two at a time stays the most accurate when the fabrics must be paired in a specific order.
What size half square triangles can I make from a charm pack?
A 5 inch charm square makes two HSTs that finish at 4 inches or smaller, since the two-at-a-time method needs squares 7/8 inch larger than the finished size. Pair a light charm with a dark one, sew on both sides of the diagonal and cut apart. For larger units, start from a 10 inch layer cake square or from yardage.
Researched from manufacturer specifications, owner manuals and verified owner reviews, not hands-on testing, and not professional advice. As an Amazon Associate, Cozy Stitchery earns from qualifying purchases.
