Quarter-Square Triangles (QSTs)
Before You Begin
Skill Level: Intermediate
Technique: Traditional Piecing
Time Required: About 15 minutes
Tools Needed: Sewing machine, rotary cutter, quilting ruler, marking pencil, iron, two Half-Square Triangles
Introduction
Quarter-Square Triangles (QSTs) are a natural progression from Half-Square Triangles. By combining two HSTs, you create a four-part unit that's used in countless traditional and modern quilt blocks, including Ohio Stars, pinwheels, and many secondary designs.
There are several ways to make QSTs, but I prefer starting with oversized Half-Square Triangles and trimming the finished unit. It provides excellent accuracy and keeps points crisp where all four pieces meet.
Step 1 – Make Two Half-Square Triangles
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Begin by making two Half-Square Triangles according to your pattern.
For best results, use oversized HSTs and trim them before creating your QST.
Step 2 – Position the HSTs
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Place the two HSTs right sides together.
Rotate one unit so the opposite fabrics are touching. The seams should nest together neatly.
Take a moment to confirm the orientation matches your pattern before sewing.
Step 3 – Mark and Sew
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Draw a diagonal line perpendicular to the existing seam.
Using a ¼" seam allowance, sew on both sides of the marked line.
Step 4 – Cut Apart
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Cut directly on the marked line.
Open the units to reveal two Quarter-Square Triangles.
Step 5 – Press and Trim
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Press the seams according to your pattern instructions.
Trim each QST to the unfinished size listed in your pattern, aligning your ruler carefully with both diagonal seams.
My Tip
Before sewing, I always fold the two HSTs open for a quick "preview" of the finished QST. It only takes a few seconds and helps catch orientation mistakes before they're stitched permanently.
Frequently Asked Questions
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Nest the seams together before sewing and pin directly through the seam intersection if needed. This helps all four points meet cleanly.
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Yes, if your pattern recommends trimming. Like HSTs, trimming improves accuracy and makes block assembly much easier.
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Yes, there are direct methods, but beginning with HSTs is often easier to understand and usually produces more accurate results.
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Follow your pattern instructions whenever a pressing direction is specified. Otherwise, press in the direction that creates the least bulk.
Continue Learning
Two-at-a-Time Half-Square Triangles
Eight-at-a-Time Half-Square Triangles
Accurate Quarter-Inch Seam Allowance
Square-in-a-Square
