On Point Quilt Calculator
Enter your block size and layout. You get the setting triangles to cut and the quilt size.
How the on point quilt calculator works
Blocks set on point are turned 45° so they sit on their corners. Each block takes up its diagonal, which is the block size × 1.414.
The gaps along the edges are filled with side setting triangles, and the four corners with corner triangles. Side triangles are cut from a square that is the block diagonal + 1 1/4", cut twice diagonally so the long edge stays on the straight grain. Corner triangles are cut from a square of (diagonal ÷ 2) + 7/8", cut once diagonally. Sizes are rounded up to the nearest 1/8". Some quilters add a little more and trim.
Questions
How many blocks in an on point quilt?
For a layout 4 blocks across and 5 down, you need 4 × 5 + 3 × 4 = 32 blocks.
Why cut side triangles from a square cut twice?
That puts the straight grain on the long outside edge of the quilt, so the edges don't stretch.
How big is a 10 inch block on point?
Its diagonal is about 14.14", so 4 blocks across makes a center about 56 5/8" wide.