SeeMyQuiltHourglass (quarter-square triangle) calculator
Enter the finished size of your hourglass unit and how many you need.
- 2 squares of each fabric make 4 hourglass units
- Each unit measures 4 1/2" before it is sewn into the block
- Prefer to trim? Cut at 5 1/2" and trim to 4 1/2"
Hourglass unit cutting chart
| Finished size | Cut squares (exact) | Cut squares (trim method) | Unit before sewing |
|---|---|---|---|
| 2" | 3 1/4" | 3 1/2" | 2 1/2" |
| 2 1/2" | 3 3/4" | 4" | 3" |
| 3" | 4 1/4" | 4 1/2" | 3 1/2" |
| 3 1/2" | 4 3/4" | 5" | 4" |
| 4" | 5 1/4" | 5 1/2" | 4 1/2" |
| 4 1/2" | 5 3/4" | 6" | 5" |
| 5" | 6 1/4" | 6 1/2" | 5 1/2" |
| 6" | 7 1/4" | 7 1/2" | 6 1/2" |
How it is calculated
Cut one square from each fabric and sew them into two half-square triangles. Do not trim them. Place the two units right sides together with the seams nested and opposite fabrics facing each other. Draw a diagonal line across the seam, sew 1/4" on each side of it, cut on the line and press.
An hourglass unit has two diagonal seams crossing in the middle, so it needs 1 1/4" of allowance in total. A 4" finished unit starts from 5 1/4" squares.
Questions
What size squares for a 12 inch Ohio Star?
The hourglass units finish at 4", so cut 5 1/4" squares: two Main and two Background for one block.
Is an hourglass unit the same as a quarter-square triangle?
Yes. Quarter-square triangle, QST and hourglass unit all describe a square made of four triangles meeting in the center.
More triangles & units calculators
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