This method of making half square triangle units has been around for a long time. It is very popular, and for good reason. It is pretty simple and eliminates the waste that occurs when doing one unit at a time.

This video steps through the technique. If you prefer written instructions with pictures, keep reading.

### Cut fabric squares

For this method, you need two squares, each an inch larger than the finished size you want. For example, if you want 4″ units, cut 5″ squares.

*If you are VERY accurate, you can get away with only adding 7/8″, but this doesn’t leave you any room for error. Most people prefer to make it a bit bigger, and trim off the extra later.*

### Mark a diagonal line

Place the two squares right sides together. On the back of one side, mark a line from corner to corner on the diagonal.

### Stitch

Sew 1/4” away from the diagonal line on each side.

*Option** 1: If it is easier, you can mark the lines 1/4” away from the centre diagonal and then sew right on the lines. This will help sewing be more accurate, but you have to mark twice as many lines.*

**Option 2:** If you don’t want to mark any lines, you can always mark a 1/4″ line on your sewing machine with tape or a laser light and align the centre of the square with that line while stitching. It is best to do this only you have some experience.

### Cut

Cut between the lines. The cutting doesn’t have to be 100% accurate, since the sewing is already done.

### Press

Open and press the seam allowances to the dark side.

### Trim

Lay your ruler on top of the square, making sure the diagonal line lines up with a 45* line on the ruler. Shave the edges off the sides to get it down to the size you need. In this case it’s 4-1/2” (finished 4” square plus 1/2” seam allowances”.

This is called “squaring up” since it gives you a chance to compensate for any potential stretching that happens when you sew along the bias. You end up with a perfectly square piece with the diagonal in the centre.

If you do a lot of half square triangles, there are specialty rulers you can get to help with this step, but I’ve never tried them. I have no problem with my regular rulers.

Trimming also removes the dog ears. Here they are – two perfect units.

#### What’s Good

- easy math to calculate cutting size
- simple to do – it makes sense
- makes two units at a time
- little waste
- perfect result

#### What’s Not Good

- drawing lines is tedious
- squaring up is more tedious

## When to use this method

- If you are using pre-cut squares
- You need a lot of HSTs
- You need an odd size

## Rating: 4 out of 5

This is one of my go-to methods for making HSTs. It is a forgiving method. Even if your cutting and stitching is not totally precise, you can still get a perfect result.

I used this method in my Rolling Meadows quilt. It is easy enough for beginners, but experienced quilters still use it.