What are Half-Square Triangles?
This odd name describes a basic quilt block made up of two triangles, one light and one dark, sewn together so they create a square with a diagonal line from corner to corner. Half-square triangles give visual excitement to quilts because of the angles they cause when pieced together in rows. This versatile design can make up any number of shapes on the quilt top, depending on which way you place the light and dark halves of the block.
Our favorite way for HST piecing
Why do we love this method? It yields 2 half-square triangles instead of one!
- Cut out squares of light and dark fabrics and pair them up, right sides together.
- Draw a diagonal line from one corner to the other on the wrong side of the light material.
- Sew ¼ inch away from this line, with one seam on each side.
- Cut along this marked line, then open up each sewn triangle to find a perfect half-square triangle.
- Press each seam allowance towards the darker fabric. Be careful to lift and press the iron, rather than move the iron around too much, remember this is the bias. Two HSTs are finished!
It just doesn’t measure up!
Sometimes, no matter how hard we try, things just don’t come out right. If that happens, double check that the original squares were cut the correct size. Then…
If the units are too small:
- Did you press correctly? Sometimes we accidentally press a tuck into the seam line in our excitement to get the project moving.
- Is your quarter inch seam accurate? Your results may be more accurate if you draw in both stitching lines 1/4″ from the center diagonal line.
If the units are too big:
- Was your seam allowance too small?
- If you drew stitching lines, were they exactly 1/4″ from the center line.
- Did you stitch exactly on the line?
If you have a lot of these shapes to make, it’s a good idea to measure the first few to test that everything is set up correctly. Then measure periodically if you’ve got oodles and oodles to make.
Half-square triangles can be used to make patchwork quilts or pinwheels. They’re also used in a variety of other quilt blocks. What are you going to make with half-square triangles?