Everything You Need To Know To Make A Half Square Triangle Quilt

Everything You Need To Know To Make A Half Square Triangle Quilt

Half square triangles (HST) are a favourite building block of many a quilter and are essential in creating beautiful intricate designs on quilts. But depending on how many HSTs you want, they can be a bit of a hassle to create in large numbers. But if you can put in the work to make them, a half square triangle quilt is often a quilting masterpiece!

An HST ruler is essential for creating triangles in the correct size, so make sure you have one on hand before starting.

If you've ever wondered how to make a quilt using HSTs, read on to find out how to make yourself a gorgeous patchwork quilt!



How to work out what size square to start with for your desired finished HST size

Using this method will create 2 HSTs every time. Rather than thinking about what size piece of quilting fabric you need to start off with, decide what size it needs to be when finished and work backwards from there. You can add between ⅞ of an inch or a whole inch to that size to give yourself some excess.


Traditional HST's Method:


Finished HST Size

Beginning Square Size


1 ⅞"


2 ⅜"


2 ⅞"


3 ⅜"


3 ⅞"


4 ⅜"


4 ⅞"


5 ⅜"


5 ⅞"


6 ⅜"


y"= x + 7/8

Make A Half Square Triangle Quilt

How to use the 1/4 inch ruler to make an HST block

The ruler is only 1/2 inch in width as the centre mark will help show 1/4 on each side.

The lines ruled by the ruler will be the sewing lines, so it helps take the guesswork out of where you need to sew.

  1. Place your 2 squares of quilting fabric together, right sides down and touching each other. Make sure the centre line of the ruler meets both corners, then draw a line down both sides of the ruler. Sew down each line and backstitch at the ends so they are secure.
  2. Cut along the central line between your stitches with a rotary cutter or scissors and you will have 2 half square triangle blocks! Press the seams open of each one. Use dry, hot steam and try not to move the iron too much, as this can stretch the fabric.
  3. Open each new block and inspect its measurements and use your cutting tools to trim down any excess.


Make A Half Square Triangle Quilt

Joining blocks together to make a half square triangle quilt

Place 2 of your HST blocks right sides together and line up the edges as best you can. Focusing on the edge that you are going to sew, fold back the corner of the top block a 1/4 inch to where the seam will be. This will allow you to see if the diagonal lines of both HST blocks are nicely lined up. Either pin the blocks in position or carefully place them under the machine and sew them together. Once sewn, open up and double check the points of both HST blocks meet perfectly in the seam line. You can use this same concept as you continue to add more blocks to your quilt, folding back the top fabric to see and align the points of your blocks.

Make A Half Square Triangle Quilt

How to sandwich a quilt and calculate backing

  1. Create and iron your quilt backing. Ensure the backing is three to four inches larger than the top part of the quilt on each side, and more if you plan on making detailed quilting stitches. This is because as the backing draws inward, more quilting stitches will need to be added.
  2. Lay the backing fabric nice and flat, right side down on the surface you are working on.
  3. Fasten the backing fabric to your work surface at even intervals. You can use pins to adhere the backing onto a carpeted surface or use wide painter's tape to stick it to a smooth surface. The backing should be flat and taut, with no wrinkles.
  4. Center a piece of your batting on top of the backing material-the batting should be around the same size as the backing. Smooth the surface of the batting with your hands to remove any bumps.
  5. Check the reverse side of the quilt top and remove any loose threads. Trim any stray long threads at the ends of your seams.
  6. Carefully centre the marked quilt top right side up on top of your batting. Once more, carefully smooth the top to flatten any wrinkles.

In a perfect world, your wadding and backing needs to be 4 inches larger on all sides compared to your top quilt. (in total, 8 inches wider and longer)

Make A Half Square Triangle Quilt

How to make your binding.

Binding is the final step in finishing a quilt. It is the fabric that is used to cover and keep intact the outer edges of a quilt. It is usually made from fabric that is cut on the bias and can be used to add another element to the quilt's design. To add binding to a quilt you will need some binding, pins, a sewing machine, your sandwiched quilt, a rotary cutter and a cutting mat.

Lay your quilt onto the cutting mat and with a rotary cutter and ruler trim your backing and wadding to meet the raw edge of your quilt top.


Attach binding to the front of the quilt:

Lay the binding along the edge of your quilt, leaving about a 10 or 12-inch tail in the binding. The longer the tail the easier it will be to join the ends of your binding together. Make sure to line up the raw edges of your quilt and the raw edge of the binding and pin in place.

Place the quilt under your presser foot and sew 1/4 inch in from the edge with a straight stitch.

You can use a standard presser foot, a walking foot or a 1/4 inch foot, there's no real right or wrong. Just use what you have and what you feel comfortable with. Start sewing, backstitch once then continue sewing for 8-10 inches. Stop and check that everything is correct.

How to mitre a corner:

Continue sewing until you reach 1/4 inch from the edge of the first corner. Measure and mark it if you want, sew to this point and then backstitch once. Cut your threads and remove the quilt from the machine.

Fold the binding up and over so there is a fold going diagonally through the middle and the edges line up along both corners. Then start sewing again from the end with a 1/4 inch seam allowance. Back stitch and continue sewing.

Your corner should look like this.

Make A Half Square Triangle Quilt

Repeat this process on all 4 corners of the quilt.

Joining the binding ends:

Lay the ends of your binding so they overlap on the edge of the quilt. You want them to overlap by 2.5 inches, so rule and mark this spot. Cut with scissors, then overlap the ends of your binding with the right sides facing in. Get your ruler and rule diagonally across the binding then pin on either side of the line and sew. Cut threads and remove your quilt from the machine.

Before you do anything, lay the quilt nice and flat and fold the binding back to check it lines up perfectly with the edge of your quilt. If you are happy, then cut the excess seam allowance back to 1/4 inch and finger press the seam open. Then finish sewing the binding down, backstitching at both ends.

Attaching the binding to the back of the quilt:

This step is optional but can be helpful. Lay your quilt flat with the right side up and iron the binding flat. This will help with pulling it to the back side of the quilt. Pull the binding over to the back side of the quilt and pin it in place around the entire edge.

You can either sew the binding down by hand or use a sewing machine. Or if you are looking for a super quick and easy option you can also use a small amount of fabric glue. Use a pin or awl to help fold the corner before sewing down. You may need to trim some of the seam allowance of the quilt if the binding isn't sitting right.

Continue sewing until the binding is sewn all the way around and your quilt is complete!

Have you caught the quilting bug now that you know how to quilt using HSTs? Why not have a go at some of our other quilting projects! All come with downloadable free quilt patterns that will help you create a gorgeous patchwork quilt every time. You can also choose from our huge range of quilting fabrics and tools online or in your nearest Spotlight store.




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