Triangles have three angles and three sides, and that means at least one edge of every triangle is cut along the fabric's stretchy bias. Handle triangles carefully to avoid stretching them out of shape.
A good portion of the triangles you'll use in your quilting projects are quick pieced, which means you won't have to fool with stretchy bias edges, but there are times when it's necessary to cut individual patches.
Let's start with half square triangles, one of the most commonly used quilting shapes.
Rotary Cut Half Square Triangles
- Cut a square that's 7/8" longer and wider than the finished length of the short sides of the triangle.
- Use your rotary equipment to cut the square in half diagonally, producing two half square triangles with the straight grains parallel to their short edges.
Corner Triangles for On Point Quilt Blocks
Half square triangles are used to make corner triangles for quilt blocks sewn on point. To determine square size:
- Calculate finished diagonal: 1.41 X finished block size
- Divide finished diagonal by 2 and add 0.875". Round the answer up to the nearest 1/8".
Example -- Corner Triangles a 10" block:
- Finished diagonal = 10" x 1.41 = 14.10"
- Square size = 14.10" / 2 = 7.05" + .875" = 7.925, round up to 8"
Square Sizes for Corner Triangles to 'Fit' Common Quilt Block Sizes
- 6" blocks, use 5-1/8" squares
- 9" blocks, use 7-1/4" squares
- 10" blocks, use 8" squares
- 12" blocks, use 9-3/8" squares
- 14" blocks, use 10-3/4" squares
