Setting Triangles Calculator
Calculate perfect cutting sizes for side and corner setting triangles in on-point quilts. Get the right measurements every time!
On-Point Quilt Layout
inches
The size of your block after sewn into the quilt
Quilt Layout:
Total blocks needed: 12 blocks
Side Triangles:
18.22"
Cut squares this size
- • Squares to cut: 4 squares
- • Cut each square: Diagonally TWICE (×)
- • Triangles per square: 4 triangles
- • Total side triangles: 14 triangles
- • Fabric needed: ~2.02 yards
💡 Important: Side triangles have straight grain on the long edge to prevent stretching on quilt edges.
Corner Triangles:
9.36"
Cut squares this size
- • Squares to cut: 2 squares (always 2)
- • Cut each square: Diagonally ONCE (÷)
- • Triangles per square: 2 triangles
- • Total corner triangles: 4 triangles
- • Fabric needed: ~0.52 yards
💡 Important: Corner triangles have straight grain on the two short edges to prevent stretching at corners.
Total Fabric Summary:
Side triangles fabric:2.02 yards
Corner triangles fabric:0.52 yards
Total setting triangles:2.54 yards
Visual Guide
On-Point Quilt Layout:
Blocks
Side Triangles
Corner Triangles
Side Triangles (Cut TWICE):
×
Cut diagonally both ways (makes 4 triangles)
Corner Triangles (Cut ONCE):
÷
Cut diagonally once (makes 2 triangles)
Why Different Cuts?
The different cutting methods ensure the straight grain (non-stretchy edge) is on the outside edges of your quilt, preventing distortion and rippling.
Setting Triangles Quick Reference
| Finished Block | Side Triangles (Cut TWICE) | Corner Triangles (Cut ONCE) |
|---|---|---|
| 6" | 9 3/4" | 5 1/4" |
| 8" | 12 1/2" | 6 5/8" |
| 10" | 15 1/2" | 8" |
| 12" | 18 1/2" | 9 1/2" |
| 14" | 21 1/4" | 10 7/8" |
| 16" | 24" | 12 1/4" |
On-Point Quilt Tips:
📐 Cutting:
- • Cut setting triangles OVERSIZED - you'll trim later
- • Mark cutting lines clearly before cutting
- • Use a large square ruler for accuracy
- • Keep triangles organized by type
🧵 Sewing:
- • Sew in diagonal rows for easier assembly
- • Press seams toward setting triangles
- • Pin triangle points to block corners
- • Don't stretch bias edges while sewing
✂️ Trimming:
- • Wait until quilt top is assembled
- • Square up entire quilt at once
- • Leave 1/4" seam allowance past block points
- • Use long ruler for straight edges
🎨 Design:
- • On-point makes quilts look larger
- • Use contrasting fabric for triangles
- • Or match triangles to background for "floating" blocks
- • Consider size - blocks look smaller on point