Square-in-a-Square
Before You Begin
Skill Level: Beginner
Technique: Traditional Piecing
Time Required: About 10–15 minutes
Tools Needed: Sewing machine, rotary cutter, quilting ruler, marking pencil, iron, one center square, four corner squares
Introduction
The Square-in-a-Square unit is exactly what its name suggests—a center square surrounded by four triangles. It's a versatile building block used in everything from traditional quilt blocks to modern geometric designs.
This version uses the stitch-and-flip method, making it beginner-friendly while producing accurate results with minimal specialty tools.
Step 1 – Prepare the Center Square
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Place one corner square on a corner of the center square, right sides together.
Draw a diagonal line from corner to corner on the wrong side of the smaller square.
Step 2 – Sew and Check
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Sew directly on the marked line.
Before trimming, fold the corner open to be sure it completely covers the corner of the center square.
If necessary, adjust the seam before trimming.
Step 3 – Trim and Press
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Trim away the excess fabric, leaving a ¼" seam allowance.
Press the triangle open.
Step 4 – Add the Remaining Corners
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Repeat the process for the remaining three corners, adding one corner at a time.
Press after each corner or after all four corners have been sewn, depending on your preferred workflow.
Step 5 – Square the Unit
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Measure the finished unit and trim if your pattern specifies.
A properly squared unit will make block assembly much easier and improve point matching throughout your quilt.
My Tip
I like to add opposite corners first, then the remaining two corners. It helps keep the block balanced while sewing and makes it easier to keep everything aligned.
Frequently Asked Questions
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The most common causes are inaccurate seam allowances or stretching while pressing. Press gently and check your seam allowance if your center square finishes too small.
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If your pattern recommends trimming, I do. Squaring the unit removes small inconsistencies and improves the accuracy of the finished block.
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Yes. Some quilters prefer to sew all four corners first, then trim and press everything together. Others prefer to complete one corner at a time. Choose the method that works best for you.
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Once the excess fabric has been cut away, it's much harder to correct a seam. Taking a few seconds to fold the corner open before trimming can save a lot of frustration later.
Continue Learning
Accurate Quarter-Inch Seam Allowance
Two-at-a-Time Half-Square Triangles
Stitch-and-Flip Flying Geese
Foundation Paper Piecing Basics
