Quarter-Square Triangle Chart
Cut sizes for quarter-square triangles and hourglass units, both ways of making them, from 1 inch up to 12. Find your finished size and read across.
Cut square = finished + 1 1/4", then cut on both diagonals
Quarter-Square Triangle Chart
getsashing.com
| Finished | Unfinished | Cut square (both diagonals) | Starting square if built from 2 HSTs |
|---|---|---|---|
| 1" | 1 1/2" | 2 1/4" | 1 7/8" |
| 1 1/2" | 2" | 2 3/4" | 2 3/8" |
| 2" | 2 1/2" | 3 1/4" | 2 7/8" |
| 2 1/2" | 3" | 3 3/4" | 3 3/8" |
| 3" | 3 1/2" | 4 1/4" | 3 7/8" |
| 3 1/2" | 4" | 4 3/4" | 4 3/8" |
| 4" | 4 1/2" | 5 1/4" | 4 7/8" |
| 4 1/2" | 5" | 5 3/4" | 5 3/8" |
| 5" | 5 1/2" | 6 1/4" | 5 7/8" |
| 5 1/2" | 6" | 6 3/4" | 6 3/8" |
| 6" | 6 1/2" | 7 1/4" | 6 7/8" |
| 6 1/2" | 7" | 7 3/4" | 7 3/8" |
| 7" | 7 1/2" | 8 1/4" | 7 7/8" |
| 7 1/2" | 8" | 8 3/4" | 8 3/8" |
| 8" | 8 1/2" | 9 1/4" | 8 7/8" |
| 9" | 9 1/2" | 10 1/4" | 9 7/8" |
| 10" | 10 1/2" | 11 1/4" | 10 7/8" |
| 12" | 12 1/2" | 13 1/4" | 12 7/8" |
1/4" seam allowance throughout. Two squares — one of each fabric — cut at the size in column three yield two hourglass units. The last column is for the alternative method: make two half-square triangles first, then recut them.
How to read the quarter-square triangle chart
Find the size the unit should finish at once it is sewn into the quilt, then cut your squares at the size in the third column. Every value is rounded up to the nearest eighth of an inch so it lands on a ruler marking.
The direct method
Cut one square of each fabric at finished + 1 1/4". Pair them right sides together, sew a quarter inch on both sides of one diagonal, cut on the drawn line, and press open — you now have two half-square triangles. Lay those two right sides together with opposite fabrics facing and the seams nested, draw a line across the seam at right angles, sew a quarter inch either side, and cut again. Two hourglass units.
The two-HST method
Some quilters find it easier to build accurate hourglasses from HSTs they have already trimmed square. Start from the size in the last column (finished + 7/8"), make and trim two half-square triangles, then recut them as above. You trim twice, so it is slower, but each unit comes out very precise.
Why the outside edges matter
The point of cutting on both diagonals is grain. It puts the straight grain of the fabric on the outer edges of the finished unit and hides the stretchy bias inside the seams. That is why you cannot simply swap in an HST-sized square and cut it twice: the unit would come out undersized and every outer edge would stretch.
Common questions
What size square do I cut for a quarter-square triangle?
Cut the square 1 1/4" larger than the finished QST size, then cut it on both diagonals. A 6" finished hourglass starts from 7 1/4" squares.
Why is it 1 1/4 inch and not 7/8 like an HST?
A quarter-square triangle puts two bias seams through the unit and lands the straight grain on the outside edges. Two diagonal seam allowances plus the trim margin come to 1 1/4", where a half-square triangle only crosses one diagonal and needs 7/8".
What is the difference between an hourglass and a quarter-square triangle?
They are the same unit under two names. An hourglass block is a square made of four quarter-square triangles, arranged so two matching triangles face each other top and bottom.
Can I make hourglass units from two half-square triangles?
Yes, and many quilters prefer it for accuracy. Build two HSTs from squares cut at finished + 7/8", lay them right sides together with opposite fabrics facing, draw a line across the seam, sew each side and cut. The last column of the chart gives that starting size.
Related
- Quarter-square triangle calculator — any size, with the yardage.
- Half-square triangle chart — the 7/8" cousin of this chart.
- Flying geese chart — the other unit built on diagonal seams.
- Printable quilt-math cheat sheet — every finished-to-cut formula on one page.
Not on the chart?
Sashing sizes hourglass units for any finished measurement, works out the yardage for both fabrics, and saves the numbers into your project.
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