Half-Square Triangle Chart
The cut size for every common half-square triangle, all three methods, on one page. Find your finished size in the first column and read across.
2 at a time: finished + 7/8" · 4 at a time: finished + 1 1/4" · 8 at a time: (finished + 7/8") × 2
Half-Square Triangle Chart
getsashing.com
| Finished | Unfinished | 2 at a time | 4 at a time | 8 at a time |
|---|---|---|---|---|
| 1" | 1 1/2" | 1 7/8" | 2 1/4" | 3 3/4" |
| 1 1/2" | 2" | 2 3/8" | 2 3/4" | 4 3/4" |
| 2" | 2 1/2" | 2 7/8" | 3 1/4" | 5 3/4" |
| 2 1/2" | 3" | 3 3/8" | 3 3/4" | 6 3/4" |
| 3" | 3 1/2" | 3 7/8" | 4 1/4" | 7 3/4" |
| 3 1/2" | 4" | 4 3/8" | 4 3/4" | 8 3/4" |
| 4" | 4 1/2" | 4 7/8" | 5 1/4" | 9 3/4" |
| 4 1/2" | 5" | 5 3/8" | 5 3/4" | 10 3/4" |
| 5" | 5 1/2" | 5 7/8" | 6 1/4" | 11 3/4" |
| 5 1/2" | 6" | 6 3/8" | 6 3/4" | 12 3/4" |
| 6" | 6 1/2" | 6 7/8" | 7 1/4" | 13 3/4" |
| 6 1/2" | 7" | 7 3/8" | 7 3/4" | 14 3/4" |
| 7" | 7 1/2" | 7 7/8" | 8 1/4" | 15 3/4" |
| 7 1/2" | 8" | 8 3/8" | 8 3/4" | 16 3/4" |
| 8" | 8 1/2" | 8 7/8" | 9 1/4" | 17 3/4" |
| 9" | 9 1/2" | 9 7/8" | 10 1/4" | 19 3/4" |
| 10" | 10 1/2" | 10 7/8" | 11 1/4" | 21 3/4" |
| 12" | 12 1/2" | 12 7/8" | 13 1/4" | 25 3/4" |
All cut sizes assume a 1/4" seam allowance. "Unfinished" is the size to trim each unit to before it goes into the quilt. Two-at-a-time and eight-at-a-time yields come in pairs from two fabrics; four-at-a-time gives four units from the same two squares.
How to read the half-square triangle chart
Find the size you want the HST to finish at — that is, the size it measures once it is sewn into the quilt with a quarter-inch seam on every side. Then pick your method and cut your starting squares at the size in that column. Every number in the table is rounded up to the nearest eighth of an inch, so it lands on a mark you actually have on your ruler.
Two at a time (the default)
Cut one square of each fabric at finished + 7/8". Lay them right sides together, draw a line corner to corner, sew a scant quarter inch on each side of the line, then cut on the line. Press, trim the dog ears, and you have two HSTs. This is the method nearly every pattern assumes when it gives you a cut size.
Four at a time
Cut one square of each fabric at finished + 1 1/4". Sew all the way around the outside, a quarter inch from each edge, then cut across both diagonals. Four HSTs. The larger addition is the quarter-square-triangle allowance, because the outer edges of these units land on the bias.
Eight at a time
Cut one square of each fabric at (finished + 7/8") × 2. Draw both diagonals, sew a quarter inch on each side of both lines, then cut the square in half vertically, horizontally, and on both diagonals — eight identical HSTs. The fastest route to a pile of matching units, and the reason the numbers in that column look so large.
Common questions
What size square do I cut for a half-square triangle?
For the two-at-a-time method, cut both squares 7/8" larger than the finished HST size. A 4" finished HST starts from two 4 7/8" squares.
Why 7/8 of an inch?
The seam runs along the diagonal, so the quarter-inch allowance on each side is measured across the bias. Two of those diagonal allowances work out to 0.707" of finished size, and the convention rounds it up to 7/8" to leave a sliver for trimming.
What is the unfinished size of an HST?
Half an inch larger than the finished size — a quarter-inch seam allowance on each of the four sides. A 3" finished HST measures 3 1/2" before it is sewn into the quilt.
Should I cut oversized and trim?
Many quilters add 1/8" to 1/4" beyond the chart and square each unit up afterwards. It costs a little fabric and buys perfectly accurate units, which matters most when several HSTs meet at one point.
Related
- Half-square triangle calculator — any size, any quantity, with the yardage.
- Quarter-square triangle chart — hourglass units, the 1 1/4" cousin of this chart.
- Half-square triangle math, explained — where 7/8" comes from.
- Printable quilt-math cheat sheet — this plus binding, borders, and precut yields on one page.
Not on the chart?
Sashing sizes HSTs for any finished measurement, adds the yardage for both fabrics, and drops the cut sizes straight into your project's cut list.
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