On-Point Quilt Calculator
Setting blocks on point (turned 45° like diamonds) leaves triangle gaps around the edges. Enter your finished block size and this free calculator gives the square to cut for the side setting triangles and the corner triangles, plus the finished quilt size, how many blocks you need and the yardage.
Setting and corner triangle sizes
Cut sizes for common finished block sizes, rounded up to the next ⅛":
| Finished block | Diagonal | Setting triangle square | Corner triangle square |
|---|---|---|---|
| 6" | 8½" | 9¾" | 5⅛" |
| 8" | 11¼" | 12⅝" | 6⅝" |
| 9" | 12¾" | 14" | 7¼" |
| 10" | 14⅛" | 15½" | 8" |
| 12" | 17" | 18¼" | 9⅜" |
How the calculator works
- Setting triangles fill the sides. Cut a square at block × 1.414 + 1¼", then cut it twice on the diagonal (an X) for 4 triangles. The long edge lands on the straight grain, so the quilt edge won't stretch.
- Corner triangles fill the 4 corners. Cut 2 squares at block ÷ 1.414 + ⅞", then cut each once on the diagonal for 2 triangles.
- Finished size. Each block on point takes up its diagonal (block × 1.414), so 5 blocks across of 10" is about 70¾" wide before borders.
- Block count. On point, the rows nest: 5 across by 6 down needs 30 blocks plus the 20 that sit in between, so 50 blocks.
Many quilters cut setting triangles a little bigger on purpose and trim after, so the blocks float. Add ½" to 1" to the setting square if you want that look.
Questions, answered
What size do I cut setting triangles for an on-point quilt?
Multiply the finished block size by 1.414 and add 1.25 inches, then round up to the next eighth. For a 10 inch block that is a 15 1/2 inch square, cut twice on the diagonal to make 4 setting triangles.
What size do I cut corner triangles?
Divide the finished block size by 1.414 and add 0.875 inches, then round up. For a 10 inch block that is an 8 inch square. Cut 2 squares once on the diagonal to get the 4 corner triangles.
How big is a quilt with blocks set on point?
Each block takes up its diagonal, which is the block size times 1.414. Multiply that by the number of blocks across and down, then add any borders. Five 10 inch blocks across is about 70 3/4 inches.
How many blocks do I need for an on-point quilt?
Multiply blocks across by blocks down, then add the blocks that sit in between: one less across times one less down. A layout 5 across and 6 down needs 30 plus 20, so 50 blocks.
Why cut setting triangles from a square cut on both diagonals?
Cutting a square twice on the diagonal puts the straight grain on the long edge of each triangle. That long edge becomes the outside edge of the quilt, so it stays straight and does not stretch or ripple.
This is one of the calculators inside Makerly.
The free version does one job well. Inside Makerly, the calculators work together: enter your quilt size once and backing, batting, binding, borders, on-point, precuts and a full printable cut list all update from the same numbers.
- Save every quilt as a project, with its numbers attached
- Design the quilt first in the Block Designer, then let the math follow
- Track your fabric stash so you know what you already own
- Works in your browser and on iPhone and Android, always in sync
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