Sashing in Quilting — What It Is, How to Calculate & Sew It

Sashing is one of those quilt design elements that can completely transform a quilt top — but many quilters skip it because they're not sure how to calculate the measurements or how to sew it in. That's a shame, because sashing is one of the easiest ways to take a quilt from "nice" to "wow." It frames each block like a picture in a gallery, gives the eye breathing room between busy designs, and can even fix the problem of blocks that aren't exactly the same size.

Whether you're adding simple strips between blocks or creating an elaborate lattice with cornerstones, this guide covers everything from the math to the sewing. Let's frame those blocks!

Key Takeaways

• ➤Sashing is all about proportion: A good sashing width is roughly 1/4 to 1/3 the finished block size. For 12" blocks, that means 2"–3" sashing. Too narrow and it disappears; too wide and it overwhelms the blocks.
• ➤Square up your blocks first: Sashing amplifies size differences. If one block is 12.25" and another is 12.75", the sashing will make that inconsistency obvious. Trim all blocks to the same size before adding sashing.
• ➤Cornerstones elevate the whole design: Small squares at sashing intersections add a professional, planned look. They also eliminate the need to match long seams precisely, making assembly easier.

What Is Sashing in Quilting?

Sashing (also called "lattice" or "lattice strips") is the fabric that separates and frames individual blocks in a quilt. Think of how a gallery wall uses matting and frames to separate individual pieces of art — sashing does the same thing for quilt blocks. Without sashing, blocks are sewn directly edge to edge, and busy or detailed blocks can visually "bleed" into each other. With sashing, each block gets its own defined space to shine.

Sashing runs both horizontally (between blocks in a row) and vertically (between rows), creating a grid pattern that holds the entire design together. The intersection points where horizontal and vertical sashing strips meet can be left plain (where the strips simply cross) or accented with small squares called cornerstones.

When to Use Sashing

Sashing Works Great When:

• Blocks are complex or busy. Detailed piecing needs breathing room. Sashing prevents neighboring blocks from competing for attention.
• Blocks are different designs. A sampler quilt (where every block is a different pattern) almost always looks better with sashing because it creates visual order from the variety.
• You want a bigger quilt without making more blocks. Adding 3" sashing to a 4×5 grid of 12" blocks adds nearly 24" of width and 27" of length. That's a significant size increase for relatively little sewing.
• Blocks aren't exactly the same size. Sashing can hide slight size variations between blocks (though you should still square up as close as possible).
• You want to feature a beautiful print. Using a gorgeous fabric as your sashing is a wonderful way to showcase it without cutting it into small pieces.

You Might Skip Sashing When:

• The design relies on blocks touching. Some patterns (like Irish Chain, Trip Around the World, or Bargello) depend on blocks connecting seamlessly to create the overall design. Sashing would break the pattern.
• You want a modern, edge-to-edge look. Many modern quilts use direct block-to-block assembly for a clean, graphic aesthetic.

Choosing Sashing Fabric

The fabric you choose for sashing makes or breaks the effect. Here are the most popular approaches:

• Solid fabric in a contrasting color: This is the most common and most effective choice. A white or cream solid makes blocks pop. A dark solid (navy, charcoal, black) adds drama and a "stained glass window" effect.
• Low-volume prints: Small, quiet prints (tiny dots, subtle textures) work like solids from a distance but add visual interest up close. Great for quilts where you want sashing that blends without being boring.
• Matching the background: Using the same fabric as your blocks' background creates a subtle, cohesive look. The sashing separates the blocks without calling attention to itself.
• Bold or patterned sashing: Using a stripe, floral, or bold print as sashing makes a strong design statement. This works best when the blocks themselves are simple.

How to Calculate Sashing Measurements

Getting the math right is the key to stress-free sashing. Here's how to calculate everything you'll need.

Step 1: Decide on Sashing Width

Choose a finished sashing width that's proportional to your block size. A good starting point:

Step 2: Count Your Strips

For a simple grid layout (blocks in rows and columns):

Step 3: Calculate Fabric Yardage

Add up the total length of all your sashing strips, divide by 40" (usable width of quilting cotton), and that gives you the number of strips you can cut from your yardage. Add 10% extra for squaring up and any cutting errors.

How to Add Sashing: Step by Step

Simple Sashing (No Cornerstones)

1. Cut all sashing strips to your calculated width and length. Cut them all at once for consistency.
2. Sew short sashing strips between blocks to create rows. Sew a sashing strip to the right side of each block (except the last block in the row). Press seams toward the sashing.
3. Measure your completed rows. They should all be the same length. If not, adjust — this is your last chance to fix size differences.
4. Cut long horizontal sashing strips the same length as your rows.
5. Sew rows and long sashing strips together, alternating row, sash, row, sash, row. Press seams toward the sashing.

Sashing with Cornerstones

Cornerstones are small squares that sit at the intersection of horizontal and vertical sashing. They add a polished, "gallery frame" look and make assembly easier because you sew in rows rather than matching long seams.

1. Cut sashing strips all the same length — equal to your unfinished block size.
2. Cut cornerstone squares — the same width as your sashing strips (e.g., if your sashing is cut at 2.5" wide, your cornerstones are 2.5" × 2.5").
3. Assemble block rows: Sew sashing strip → block → sashing strip → block, ending with a sashing strip. Press toward sashing.
4. Assemble sashing rows: Sew cornerstone → sashing strip → cornerstone → sashing strip, matching the width of your block rows. Press toward sashing strips.
5. Sew block rows and sashing rows together, alternating. The cornerstones should line up with the vertical sashing strips.

Creative Sashing Ideas

• Pieced sashing: Instead of plain strips, use strip-pieced sashing (like a piano keys design) for extra visual interest.
• Different-width sashing: Use narrower sashing between blocks in a row and wider sashing between rows (or vice versa) for an asymmetric, modern look.
• Partial sashing: Add sashing only between rows (horizontal sashing) but not between blocks (no vertical sashing). This creates a banded effect.
• Double sashing: Use two narrow strips of different colors side by side for a more elaborate frame effect.
• Sashing with inner borders: Add a thin inner border (1/2"–1" finished) around each block before the main sashing. This "frames the frame" and works beautifully with sampler quilts.

Common Sashing Mistakes

• Not squaring blocks first. Sashing highlights size differences. If Block A is 12.3" and Block B is 12.7", the sashing will wave and pucker. Always trim all blocks to the same unfinished size before adding sashing.
• Cutting sashing strips individually. Cut all your strips in one batch from the same fabric to ensure consistent width. Even a 1/16" variation in strip width adds up across multiple rows.
• Stretching sashing to fit. If a sashing strip doesn't quite reach, don't stretch it — recut it. Stretched fabric creates wavy seams that compound across the quilt.
• Forgetting to press toward the sashing. Press seam allowances toward the sashing strips (and away from blocks). This reduces bulk in the blocks and makes nesting seams easier when joining rows.
• Using sashing that's too narrow. Under 1" finished, sashing almost disappears. Unless that's the look you want, go at least 1.5" finished for a visible frame effect.

Frequently Asked Questions

How much fabric do I need for sashing?

For a throw-size quilt (4×5 blocks, 12" each, with 2.5" cut sashing): roughly 1.5 yards. For a queen-size (5×6 blocks): roughly 2.5 yards. Add more if using cornerstones from the same fabric. The exact amount depends on your layout — use the formulas above to calculate precisely.

Can I use sashing with any block?

Almost any! The only exception is designs that depend on blocks connecting seamlessly (like Trip Around the World or Bargello). For sampler quilts, scrap quilts, and any quilt with distinct, self-contained blocks, sashing is a wonderful addition.

Should sashing be the same width as borders?

Not necessarily. It's common for borders to be wider than sashing — 3"–4" borders with 2" sashing, for example. But keeping them in proportion creates a harmonious design. As a starting point, try borders that are 1.5× your sashing width.

What about sashing on quilts with on-point (diagonal) settings?

Sashing works beautifully with on-point quilts! The strips run diagonally between the tilted blocks. The math is the same — just remember that your setting triangles (the half-blocks around the edges) will also need sashing strips on their open sides. On-point sashing creates a stunning diamond-lattice effect.