Quilters use this triangle cutting chart when piecing a diagonal layout quilt. In a diagonal layout, blocks are placed on-point. The blocks are shown in white above. The corner triangles, shown in black, are in the corners. Side triangles, shown in gray, are along the edges.
Cutting Triangles from Squares
This triangle cutting chart is based on cutting squares then sub-cutting the squares into triangles.
Cut the square twice diagonally for side triangles.
Cut the square once diagonally for corner triangles
Why Cut Triangles from Squares?
Squares are easy to cut. First, cut along the width of fabric. Next, sub-cut into squares. Finally, sub-cut the squares into 2 or 4 triangles. Cutting squares this way ensures the grain lines follow the outer edges of the quilt. The picture below shows the grain lines for the side triangle cuts. These cuts put either the crosswise or lengthwise grain along the outside edges of the quilt.
Next we have a picture of the grain lines for the corner triangle cuts. These cuts also put the grain lines along the outside edges of the quilt.
How to Use the Triangle Cutting Chart
Step 1 - First, find the finished block size in column 1.
Step 2 - Next, find the corresponding number in column 2. Cut squares to this size in inches. One square gives you 4 side triangles. Step 3 - Finally, find the corresponding number in column 3. Cut 2 squares to this size in inches. One square gives you 2 corner triangles.
NOTE: When in doubt about what size to cut, always round UP just to be sure. You can always trim it down later.
If you prefer to do the math yourself, here are the formulas:
(Finished block size in inches x 1.414) + 1.25"
(Finished block size in inches / 1.414) + .875"