HST formulas by method
- 2 at a time: cut square = finished size + ⅞". Draw a diagonal, sew ¼" either side, cut on the line.
- 4 at a time: cut square = (finished size + ½") × 1.414. Place two squares right sides together, sew ¼" around the outside edge, then cut both diagonals.
- 8 at a time: cut square = (finished size + ⅞") × 2. Sew ¼" either side of both diagonals, then cut horizontally, vertically and on both diagonals.
Example: for 3" finished HSTs, cut 3⅞" squares for 2-at-a-time (4" if you want to trim), 5" squares for 4-at-a-time (3½ × 1.414 = 4.95, rounded up; 5⅛" to trim), or 7¾" squares for 8-at-a-time (8" with a trimming margin). Every method gives a 3½" unfinished unit.
HST cut size chart
Square sizes to cut, with the trimming margin unless noted.
| Finished | Unfinished | 2 at a time (exact) | 2 at a time (trim) | 4 at a time | 8 at a time |
|---|---|---|---|---|---|
| 1" | 1½" | 1⅞" | 2" | 2¼" | 4" |
| 1½" | 2" | 2⅜" | 2½" | 3" | 5" |
| 2" | 2½" | 2⅞" | 3" | 3¾" | 6" |
| 2½" | 3" | 3⅜" | 3½" | 4⅜" | 7" |
| 3" | 3½" | 3⅞" | 4" | 5⅛" | 8" |
| 3½" | 4" | 4⅜" | 4½" | 5⅞" | 9" |
| 4" | 4½" | 4⅞" | 5" | 6½" | 10" |
| 5" | 5½" | 5⅞" | 6" | 8" | 12" |
| 6" | 6½" | 6⅞" | 7" | 9⅜" | 14" |
Getting accurate HSTs
- Use a scant ¼" seam. A thread or two narrower than ¼" makes up for the fold of fabric at the pressed seam.
- Press before you trim, then line up the 45° line on your ruler with the diagonal seam.
- Starch helps with 4- and 8-at-a-time units, whose outer edges are on the bias and stretch easily.
- Setting blocks on point? The setting triangle calculator handles the edge triangles.