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Half Square Triangle Infinity Scarf Tutorial

This simple patchwork scarf has quickly become my go-to accessory for chilly days in Colorado. For beginners, the half square triangles are a great introduction to a versatile piecing technique, and seasoned sewists will whip this up in no time!

Caitlin holding up her Half Square Triangle Infinity Scarf


¾ yd Fabric A - Moda Ninepatch Flannel in Cornflower Blue
½ yd Fabric B - Sateen Fuccra Rakuen in Cloud
¼ yd Fabric C - Beau Pocho Lawn In Cream
¼ yd Fabric D - Solid Gauze in Ochre
Water-soluble marking tool
Rotary Cutter
Quilting Ruler
Cutting Mat

Caitlin Vannoy wearing her Half Square Triangle Infinity Scarf from Nani Iro sateen

Before you begin, cut the following

Cut 6 - 7 ⅜” squares from Fabric B
Cut 3 - 7 ⅜” squares from Fabric C
Cut 3 - 7 ⅜” squares from Fabric D

Seam Allowance: ½” unless otherwise specified

Sew your half square triangles:

Pair up one B square with one C square, right sides together. Align the edges and mark a diagonal line between one corner to the opposite corner. Pin to secure.

Sew a ¼” from the diagonal line. Repeat along the other side of the line so there are two seams.

Cut along the diagonal line you marked in step 1.

You will now have two half square triangle blocks.  Press the seam allowance to one side (toward whichever fabric is darkest or the least see-through).

How to sew a half square triangle

Using your rotary cutter and quilting ruler, remove the dog ears. Your blocks should now be 7” x 7”.  

Repeat Steps 1-5 with the remaining B, C, and D squares.  You will now have 12 blocks total.

Arrange the 12 blocks in a 4 x 3 grid.  Work one row at a time, and sew the blocks together by placing right sides together and sewing with a ½” seam allowance. (Please note: normally you’d be piecing HSTs with a ¼” SA, however, since we are not quilting these down, I like the added insurance of a bigger SA). Press the seams open.

Pick the layout you want for your Half Square Triangles

Continue until you have complete rows, then connect the rows by placing them right sides together and sewing a ½” seam allowance. Press the seams open.

The width of the 4 blocks sewn together should now be 25”.  Take a moment to double check this measurement along the long edge of the patchwork. If it is not 25”, don’t fret! HSTs take practice and your cozy new scarf won’t judge. Whatever that measurement is, you will not trim up Fabric A to be that wide (25”) x 44” (or the length from selvedge to selvedge).  Trim off your selvedges on either side.  

    Black and White Nani Iro Linen Half Square Triangle Infiniti Scarf

    Assemble your scarf:

    Align the long edge of your patchwork with the corresponding width of Fabric A, right sides together. Secure along the edge with pins, and sew with a ½” SA. Press seam open.

    Lay Patchwork down on the short side of your main fabric

    You now have a long, skinny rectangle with patchwork at one end.  Fold this, right sides together, lengthwise. Line up the edge and align the seams from your patchwork. Pin in place and sew along the long edge with a ½” SA.  Press the seam open (this can be tricky because you now have a long tube, but I found it helpful to use a sleeve ironing board).

    Pin and sew the long edge of your scarf together

    With the tube inside out, but push one end into the tube to match up the two unfinished ends right sides together. Line up the raw edges, aligning the side seam and pin in place. Take care not to twist the tube. With a ½” seam allowance, sew along the edge, but leave a 4” gap to turn right side out.

    Make the short ends of your scarf meet up right sides togetherSew around the unfinished ends of your scarf leaving a 4" gap un-sewn

    Pull the right side out through the gap you left in step

    Pull the scarf so right sides are facing out

    Hand stitch the hole closed and give it a good press.  Congratulations! You just completed your Half Square Triangle Infinity Scaf. Share your results with us using #hstinfinityscarf

      Finished Half Square Triangle Infinity Scarf

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