The Split Quarter Square Triangle Quilt Block is a variation of the Quarter Square Triangle block, which is also referred to as the Hour Glass quilt block.

What makes it the Split Quarter is that one half of the block is one fabric, and the other half of the block is two different fabrics. It’s like a split half square triangle block.

The block contains one half-square triangle and two quarter-square segments to complete the square unit. This is used in many star quilt blocks, such as the Air Castle Quilt Block.

Split quarter square triangle finished block graphic

Split Quarter Square Triangles Fabric Calculator

Since this block is partially a half square triangle, and partially a quarter square triangle, we’ll use the same calculations. For the half that is one fabric (see fabric 1 above), cut squares that are 7/8″ larger than the finished size. For the half that are two fabrics (see fabrics 2 and 3 above), cut squares that are 1-1/4″ larger than the finished size. Here is a chart with common sizes:

To make 4 finished blocks, cut the following:
2″ finished size: Cut 1 square each from two fabrics at 3-1/2″ for quarter squares; cut 2 squares at 2-7/8″ for half squares.
3″ finished size: Cut 1 square each from two fabrics at 4-1/4″ for quarter squares; cut 2 squares at 3-7/8″ for half squares.
4″ finished size: Cut 1 square each from two fabrics at 5-1/4″ for quarter squares; cut 2 squares at 4-7/8″ for half squares.
5″ finished size: Cut 1 square each from two fabrics at 6-1/4″ for quarter squares; cut 2 squares at 5-7/8″ for half squares.
6″ finished size: Cut 1 square each from two fabrics at 7-1/4″ for quarter squares; cut 2 squares at 6-7/8″ for half squares.
And, so on . . .

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The unfinished size for each of the blocks above will be 1/2″ larger than the finished size. Sew them together with a 1/4-inch seam allowance.

Four (4) finished quilt blocks

How to Make the Split Quarter Square Triangle Quilt Block

Prep Time: 10 minutes

Active Time: 20 minutes

Total Time: 30 minutes

Difficulty: Intermediate

The Split Quarter Square Triangle quilt block is a variation of the Quarter Square Triangle and can be used as a stand-alone block or in combination with other blocks.

This is my preferred method to make this quilt block as you aren't trying to sew bias edges together. You sew along both sides of a drawn diagonal to make the diagonal seam. Bonus: there is very little fabric waste.

No special rulers are needed!

Here is our free tutorial to make the split quarter triangle block:

Materials

Three (3) different fabrics
Thread

Tools

Sewing machine
Iron
Ironing Board
Rotary cutter
Cutting mat
Quilters Rulers
Marking tool, I used a Frixion pen

Instructions

Use your quilting ruler and rotary cuter to cut your fabrics according to the cutting chart above. I made 3" finished quilt blocks, so I cut two fabrics at 4-1/4" and two squares from the third fabric at 3-7/8".
Start by making half-square triangles from your larger cut squares. These will make the quarter triangle side of the block. Using a removable fabric marker, draw a diagonal line on the wrong side of one fabric.
Layer on top of the other larger cut square right sides together and sew 1/4" from the diagonal line. I use the 1/4-inch presser foot to make sure I sew an accurate seam.
Turn and sew 1/4" from the other side of the marked line.
Cut along the marked line to form two squares. These are basic HST blocks.
Press open.
Mark the diagonal on the wrong side of the third fabric. Layer it on top of the pieced square with the the marked line 90 degrees from the stitched seam on the half square triangles.
Sew 1/4" on both sides of the line, just as before. Cut along the marked line.
Press and you have split quarter triangle quilt blocks! Note: these are two sets of blocks - they are not all the same! Note how the rows have the quarter square sides reversed. This will make a difference in some quilt blocks! You might need to double the number of Split Quarter Square Triangle Quilt Blocks you make. as I did here Use them in another piece, or on the back!
Here is how it looks to put the four pieces together for a finished quilt block.

Notes

Before using in a quilt block, use a square ruler to trim up your block and cut off the dog ears.

The split quarter square triangle is a great building block for many popular patchwork designs and patterns.

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Tips and ideas for making the split quarter square triangle quilt block

This method makes two blocks at a time. The two blocks are mirror images of each other. You may need to make more than you need to get the layouts and colors right for your finished quilt block.
Use charm packs or layer cakes to get started on these blocks.
Pay attention to your fabric choices. To make the design pop, use different contrasting fabrics – either color choices or designs or both.
When trimming the finished squares, where the small triangles meet should be in the center of the block, the center point and be at a 45-degree line with the other half of the block.