Sawtooth Quilt Block Pattern

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How to Sew a Sawtooth Quilt Block

The Sawtooth block uses half-square triangles (HSTs) arranged to create a bold zigzag or sawtooth edge design. It's a classic pattern that works beautifully in both traditional and modern quilts.

Materials You Will Need

• Fabric (at least two different colors or prints)
• Ruler
• Rotary cutter or fabric scissors
• Sewing machine
• Iron and ironing board
• Pencil or fabric marker

Step-by-Step Instructions

1. Cut two squares of fabric to the same size. For example, cut 5" squares for a 4" finished block.
2. Place the two squares right sides together, edges aligned.
3. Draw a diagonal line from one corner to the opposite corner on the back of the lighter square.
4. Sew a ¼" seam on both sides of the marked line.
5. Cut along the marked line to separate the two HST units.
6. Press the seams open on each unit.
7. Trim the dog ears (the small triangles that stick out beyond the seam) from each unit.
8. Arrange the HST units in the Sawtooth layout, right sides together with seams matched.
9. Sew a ¼" seam to join the units into rows, then join the rows together.
10. Press the seams open and trim the block to the desired size.
11. Repeat to create as many Sawtooth blocks as needed for your quilt.

Half-Square Triangle (HST) Technique

This technique eliminates the need to directly manipulate the stretchy bias of the triangle. It uses two easy-to-cut squares and produces two HSTs at once.

Step 1: Draw the Diagonal Line

On the back of the lighter fabric, draw a pencil line diagonally from corner to corner.

Step 2: Sew Both Sides of the Line

Stack a pair of light and dark squares right sides together. Sew a ¼" seam allowance on each side of the line.

Step 3: Cut and Open

You will end up with something like this:

Now cut along the diagonal line.

Step 4: Press the Seam

Press the seam together to set it, then press toward the darkest fabric.

Step 5: Trim to Size

To trim the block to the exact size, line up the 45° diagonal angle on your ruler with the seam.

Then carefully trim your block with a rotary cutter.

How to Resize Quilt Blocks

The first step in modifying any quilt block is to decide on your finished block size. You can base this on doubling a pattern, cutting it in half, or working with your available fabric.

Note: When working from a pattern's cutting instructions, remove the seam allowance before scaling. For example, if your pattern calls for 3½″ squares, subtract the seam allowance (½″), double the finished size (3″ → 6″), then add the seam allowance back (½″) — giving you a 6½″ cut piece.

Resizing Square Blocks

Add ½″ to your finished block measurement. For a 4″ finished square, cut a 4½″ square of fabric.

Resizing Rectangular Blocks

Add ½″ to both the length and width. To double a 3″ × 4″ block, cut a 6½″ × 8½″ rectangle.

Resizing Half-Square Triangle Blocks

Add 7/8″ to the desired finished block size. For a 4″ finished HST block, cut 4⅞″ squares.

Resizing Quarter Square Triangle Blocks

Add 1¼″ to the desired finished block size. For a 4″ finished block, cut 5¼″ squares.