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Cutting dimensions for HRT units at any finished size, using the no-special-ruler stitch-and-trim method.
For 4″ × 2″ finished HRTs, cut 5″ × 3″ rectangles — one of each fabric per pair — and trim each unit to 4½″ × 2½″.
Layer a pair right sides together, draw corner to corner, sew ¼″ each side of the line, cut on the line: 2 units with the same slant. For mirror-image units, draw the diagonal the other way on half your pairs.
| Fabric | Rectangles | Per fat quarter | Fat quarters | Or yardage |
|---|---|---|---|---|
| Fabric A | 8 | 25 | 1 | ¼ yd (1 strip) |
| Fabric B | 8 | 25 | 1 | ¼ yd (1 strip) |
8 pairs → 16 units. Yardage assumes 40″ usable width; fat quarters assume 18″ × 21″ after trimming.
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| Finished Size (W×H) | Cut Two Rectangles |
|---|---|
| 2″×1″ | 3"×2" |
| 3″×1.5″ | 4"×2-1/2" |
| 4″×2″ | 5"×3" |
| 6″×3″ | 7"×4" |
| 8″×4″ | 9"×5" |
| 10″×5″ | 11"×6" |
| 12″×6″ | 13"×7" |
Each pair of rectangles yields 2 HRT units. Trim down to the exact finished + seam allowance size after sewing and cutting apart — this method deliberately oversizes the cut, unlike a true half-square triangle.
High-contrast solids or tone-on-tones make the diagonal read clearly.
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Using the stitch-and-trim method (no specialty ruler), cut two rectangles 1" larger than the finished size in both directions. For a finished 4"×2" HRT, cut two 5"×3" rectangles. This yields 2 HRT units per pair, trimmed down after sewing.
Layer two contrasting rectangles right sides together. Draw a diagonal line from one corner to the opposite corner. Sew 1/4" from the line on both sides, then cut apart on the drawn line. Press the seam open or to one side, then trim each unit down to its exact finished size plus seam allowance using a square-up ruler — this step removes the excess from the oversized cut.
An HST is cut from a square, so the diagonal is a perfect 45° line and the math reduces to one clean add-7/8" formula. An HRT is cut from a non-square rectangle, so the diagonal isn't 45° and the seam allowance doesn't reduce as neatly — the stitch-and-trim method compensates by cutting oversized and trimming to the exact size afterward, at the cost of some fabric waste.
If you're making many HRTs at one size, a specialty ruler (e.g. a rectangle/HRT-specific ruler) cuts closer to the finished size with far less trimming waste and no drawn line needed. The stitch-and-trim method in the table above needs no special tools and is the better choice for a one-off block or trying HRTs for the first time.