How to Quilt: Half Square Triangles

How to Quilt: A Beginner's Guide 12-week sew along

Welcome to the second week, and the second project, of How to Quilt: A Beginner’s Guide. This week we’re learning how to make a Half Square Triangles block. From there, we’ll mount the block on a canvas to create a work of art ready to hang on the wall.

To get started, we’ve made a playlist of uquilt videos that show you pre-sewing skills, how to sew a half square triangle, how to size a half square triangle and more. Take a moment to watch and review. Be sure to refer to your sewing machine’s manual for specific threading and setup guidance. We add skills videos relevant to the projects before each project in the playlist, so be sure to scroll through for the related skills.

Now that we’re caught up on our skills, let’s make a Half Square Triangle Canvas!

Follow along with the written instructions below.

Half Square Triangle Canvas

half square triangle

The fabrics to make the Half Square Triangles Canvas pictured above are part of the How To Quilt Fabric Bundle, which includes all the fabrics for the series. There’s also a starter kit with sewing and quilting supplies.

Fabric/Supply Requirements

1/4 yard of Light Value fabric
1/3 yard of the Dark Value fabric
1 pre-made 12″ x 12″ art canvas
Light duty staple gun and staples

Cutting Instructions

From the Light Value fabric, cut:
(2) 3″ x Width of Fabric (WOF) subcut into:
(18) 3″ x 3″

From the Dark Value fabric, cut:
(2) 3″ x Width of Fabric (WOF) subcut into:
(18) 3″ x 3″
(2) 3″ x 12 1/2″
(1) 3 1/2″ x Width of Fabric

Note: We recommend using a 1/4″ foot to assemble this project, but if you don’t have one try marking your 1/4″ seams on the wrong side of the fabric with a ruler and pencil.

Cutting Notes

Cut (2) 3″ strips from the Light Value fabric. For the first strip, cut off the selvage to make a straight cut, and then measure 3″ increments and cut the strip into 3″ squares. Repeat with the second strip until you have (18) 3″ squares.

Cut (3) 3″ strips from the Dark Value fabric. Cut the first and second strips in the same manner as the Light Value strips. With the excess from the second strip, cut (2) 3″ x 12 1/2″ rectangles. Cut the third strip in half along the fold.

Half Square Triangles

Mark the wrong side of a light value 3″ square in half diagonally once. Lay a marked light value 3″ square over a dark value 3″ square, right sides together. Sew a quarter inch from each side of the marked line. Cut apart on the marked line and press towards the dark.

Lay a ruler over the Half Square Triangle lining up the seam on a 45 degree line to the corner of the ruler. Shift the ruler so everything is straight, make sure there is more than 2 1/2″ of fabric under the ruler and trim the side and top. Turn the Half Square Triangle to the untrimmed sides. Line the ruler up along the straight cut sides to 2 1/2″ and trim excess fabric. This process is called sizing.

Make 36 Half Square Triangles and size them all to 2 1/2″ unfinished.

Half Square Triangle Art

Using either a design wall tool like the Prop It or a clear space near your sewing machine, lay out the Half Square Triangles into a grid 6 x 6. Arrange the Half Square Triangle into a pleasing design. We have some ideas below to get you started.

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Once the Half Square triangles are arranged, layer the first two Half Square Triangles in the first row right sides together and sew a quarter inch seam on the side where they meet. Press towards the right and repeat with the next Half Square Triangle in the sequence. Sew the next row in the same manner, but press towards the left. Make 6 rows according to your layout, alternating the direction the seams are pressed.

Each row should measure 2 1/2″ x 12 1/2″ unfinished. If yours is smaller, try taking a narrower quarter inch seam. If yours is larger, try taking a wider quarter inch seam.

Lay the first and second row right sides together and sew a quarter inch seam on the side where they meet. Press in one direction, pressing first lightly from the front to get all the fabric away from the seam, and then pressing longer from the back to make it lay flat. We do this to prevent scorching the front of the block with the longer press the thick seam intersections require.

The block should measure 12 1/2″ x 12 1/2″ unfinished.

Fabric Frame

Layer a dark value 3″ x 12 1/2″ strip and the Half Square Triangle block with the strip on bottom. Sew a quarter inch seam. Repeat on the opposite side. Press towards the dark value strips.

Layer the one of the cut in half on the fold 3″ strips and the block with the strip on bottom. Sew a quarter inch seam. Repeat on the other side. Press towards the dark value strips and trim the ends even to the other dark value strip. Accurate trimming isn’t a concern at this step. This completes the frame.

Mounting the Block On an Art Canvas

Clear a clean, sturdy work surface. Lay the block pretty side down on the work surface. Place the right side of the art canvas on top of the wrong side of the block. Center the canvas on the block. Pull up the fabric frame in the center of one side, being careful not to shift the canvas placement, and staple the frame to the wood of the canvas. Repeat on the opposite side in the center, and make sure to pull the block taut. Repeat on all sides. Staple the sides in this manner until only the corners remain unstapled.

Pinch the fabric frame together at the corners and trim the tips off at a 45 degree angle. Pull one side over and staple it. Manipulate the fabric into a 45 degree angle fold and staple. Next, pull over the other side so no fabric sticks out past the canvas, and staple. Repeat on the remaining corners to complete your Half Square Triangle Canvas.

Now, you just have the find the perfect place to display your artwork!

Want more practice with Half Square Triangles?

Check out the Jungle Fever Half Square Frenzy quilt made from 10″ pre-cut squares, a free pattern from AQSblog.

Ready to join a community of beginners, share your progress and get exclusive tips?

Join the How To Quilt AQS Facebook group. We can’t wait to see what you make!

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