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Cut sizes for every finished HST size, two-at-a-time and four-at-a-time methods, and yield per fat quarter.
For 3″ finished HSTs (3½″ unfinished), cut 3⅞″ squares — one of each fabric per pair.
Layer a pair right sides together, draw the diagonal, sew ¼″ each side of the line, cut on the line: 2 HSTs. Trim each unit to 3½″.
| Fabric | Squares | Per fat quarter | Fat quarters | Or yardage |
|---|---|---|---|---|
| Fabric A | 8 | 20 | 1 | ¼ yd (1 strip) |
| Fabric B | 8 | 20 | 1 | ¼ yd (1 strip) |
8 pairs → 16 HSTs. Yardage assumes 40″ usable width; fat quarters assume 18″ × 21″ after trimming.
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Two-at-a-time: Cut size = finished HST size + 7/8″. Mark diagonal, sew 1/4″ on both sides, cut on diagonal → 2 HSTs per pair.
Four-at-a-time:Two squares at (finished + 7/8″) × 1.414, sewn together around all four edges, cut on both diagonals → 4 HSTs.
Eight-at-a-time:Two squares at 2 × (finished + 7/8″), sew 1/4″ either side of both diagonals, cut on both diagonals and through the center → 8 HSTs.
| Finished HST | Cut (2-at-a-time) | HSTs per FQ |
|---|---|---|
| 1" | 1⅞" | 198 |
| 1½" | 2⅜" | 112 |
| 2" | 2⅞" | 84 |
| 2½" | 3⅜" | 60 |
| 3" | 3⅞" | 40 |
| 3½" | 4⅜" | 32 |
| 4" | 4⅞" | 24 |
| 4½" | 5⅜" | 18 |
| 5" | 5⅞" | 18 |
| 6" | 6⅞" | 12 |
| 8" | 8⅞" | 8 |
| 10" | 10⅞" | 2 |
FQ yield based on a 21″×18″ fat quarter after trimming, two-at-a-time method (each square pairs with one from a second fabric). Trim all HSTs after sewing for accuracy.
Fat quarter bundles are the fastest way to a coordinated set of HST fabrics.
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For a 3-inch finished half square triangle using the two-at-a-time method, cut squares at 3-7/8 inches. Mark a diagonal line on the wrong side of one square, sew 1/4" on both sides of the line, and cut on the diagonal. You get 2 HSTs per pair of squares, each finishing at 3 inches.
For the two-at-a-time method: cut size = finished HST size + 7/8". For the four-at-a-time method: cut two squares at (finished size + 7/8") × 1.414 — a 3" finished HST starts from two 5-1/2" squares. For eight-at-a-time: cut two squares at 2 × (finished size + 7/8") — 7-3/4" for a 3" HST. All three give HSTs that trim to the exact finished size.
Cut two squares, one of each fabric, at (finished size + 7/8") × 1.414 — use the table below. Place them right sides together and sew 1/4" from the edge all the way around all four sides. Cut on both diagonals. The four triangles open into 4 HSTs with the seams on the bias, so handle them gently and trim to finished size + 1/2". For 8 at a time, start with squares at 2 × (finished + 7/8"), sew 1/4" on both sides of both diagonals, then cut on the diagonals and through the center both ways.
HSTs usually need to be trimmed after sewing. Use a square ruler with a 45-degree diagonal line: align the line on the seam and trim two sides, then rotate and trim the remaining two sides. The most common causes of off-size HSTs are an inaccurate 1/4" seam allowance and not pressing before trimming.