Quarter Sq Triangles

Learn all about quarter square triangles, where they are used and why as well as making quarter square triangle blocks.

qst QST

What are Quarter Square Triangles?

A Quarter Square Triangle is a square that is cut through the diagonal twice to give four triangles. 

Four half square triangles make a square.

qst QST block

How are quarter square triangle blocks made?

Cut squares of fabric the required size. For this lesson we will use 3 1/4" squares. 

There are two steps to making Quarter Square Triangle blocks. 

Step One: Make a Half Square Triangle as described in our Half Square Triangle lesson at: Half Square Triangle Instructions

Press your half square triangle open but do not trim. 

qst QST step2Step Two: Place two Half Square Triangle blocks together so seams are matching directly on top of each other.

Draw a diagonal line through the block opposite to the seam, and stitch 1/4" from drawn line on both sides.

Cut along drawn line and press as describe for Half Square Triangle block. 

Trim to 2 1/2" matching lines on ruler with seam.

qst block with QSTHow do you determine the cutting size?

Add 1 1/2" to the finished size of the block. This example shows a 4" block. A Quarter square triangle block (outlined in red) for this is 2", therefore cut each square 3 1/2".


Where else do we use quarter square triangle?

qst setting trianglesQuarter square triangles are also used for the setting triangles of a quilt made where blocks are on-point (outlined in the green triangle). Here we just use single triangles so they are cut before stitching.

Do we also use single quarter square triangles for the corner setting triangles of a quilt made with blocks on-point?

No. We use half square triangles for this (half square triangle is outlined in red). Check below to find more information about half square triangles.

Check out some of our patterns that use quarter square triangles.

Check out our other free lessons and online classes

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