Half-Square Triangle Technique
Many of us avoid
making quilts that have half-square triangles. Why? – because cutting out the triangle shape
pieces and sewing them together on the bias can result in very few coming out the correct size.
The method described in this blog can be used anytime you need two or more of these squares
for a project.
Layout and cut larger than called for –
When creating the layout for sewing the diagonal lines, I add 1 inch to the finished size of the
half-square triangle unit, instead of the recommended 7/8 inch. Remember, the finished size is
what shows after the block is sewn to other blocks. When cutting to separate the blocks, add
1/2 inch to the finished size. If your finished square is supposed to be 2 ½ inches, you will trim
each unit to 3 inches, creating a ¼ inch seam allowance.
Gridded Fabric Method –
1. Using the desired finished size of a square, calculate the number of triangles you require for
your project. Determine the layout size of each square of the grid (remember 1 inch larger
than the finished size). Determine the total size of fabric required to create the number of
triangles you need.
2. Cut two pieces of fabric one inch larger in each direction than the total size of fabric
determined in step 1. Stack the large fabric pieces with right-sides together.
3. Use a ruler and pencil to mark a grid on the light colored fabric as shown above. Remember
to allow some extra fabric on each edge of the grid.
4. Draw in the diagonal cutting lines.
5. Sew a 1/4” stitch line on both sides of the cutting lines. (Note, the red dashed lines do not
need to be drawn on your fabric, they were added to clarify where the stitch lines should be.)
6. Using a rotary cutter and a ruler, cut on the lines that are parallel to the edges of the of the
fabric grid.
7. Then cut on the diagonal lines between the stitched lines.
8. With the seam allowances folded towards the darker of the two fabrics, finger press open
each pieced square.
9. Trim the fabric units so you have neatly finished squares.
10. You will end up with two equal-sized half square triangle units from each square on your
grid.