What is Sashing in Quilting? A Complete Guide

What is sashing, exactly?

Sashing is the fabric that goes between quilt blocks. Think of it like the leading in a stained glass window — it separates and frames each individual block. Sashing strips run vertically and horizontally between your blocks, and they're sewn in during the quilt top assembly phase, after your blocks are done but before borders go on. Without sashing, blocks are sewn directly to each other, which creates a very different look. Neither approach is better — it depends entirely on what you want the finished quilt to feel like.

Why do quilters add sashing?

Sashing serves several practical and aesthetic purposes that make it worth considering for almost any quilt project.

• It visually separates blocks so each one reads as its own design, which is especially useful with complex or high-contrast blocks.
• It adds size to a quilt without making more blocks — a 2-inch sashing on a 12-block quilt can add 6+ inches to the overall width and height.
• It gives your eye a place to rest between busy blocks. If you're using lots of prints, sashing in a solid fabric calms the whole quilt down.
• It hides slight size differences between blocks. If your blocks aren't perfectly identical (and nobody's are), sashing is forgiving because it absorbs small discrepancies.
• It creates a design grid that makes the quilt feel more intentional and structured.

Types of sashing

There are three main types of sashing, and each gives your quilt a different feel. Plain sashing is the simplest: solid strips of fabric cut to the same width and sewn between every block. Most beginners start here, and honestly, most experienced quilters use it too. It's clean and effective. Pieced sashing uses patchwork strips instead of solid fabric — you might see flying geese, half-square triangles, or chain blocks forming the sashing itself. This adds a lot of visual interest but requires more planning and more fabric. Sashing with cornerstones adds small squares at the intersections where vertical and horizontal sashing strips meet. Cornerstones are usually a contrasting fabric and create a grid-like appearance. This is probably the most popular sashing style because it's almost as easy as plain sashing but looks much more polished.

How wide should sashing be?

There's no single right answer, but here are guidelines that work well. For 12-inch blocks (finished), 2 to 3 inches of sashing is the sweet spot. For smaller blocks (6–9 inches), 1.5 to 2 inches keeps things proportional. For large blocks (15+ inches), 3 to 4 inches works nicely. A common mistake is making sashing too narrow — anything under 1.5 inches (finished) tends to look like a seam rather than an intentional design element. When in doubt, cut a test strip and lay it next to your block before cutting all your fabric.

How to calculate sashing yardage

Sashing yardage is straightforward once you break it into strips. Count how many vertical sashing strips you need (one between each column of blocks, plus optionally the outside edges). Count horizontal sashing strips the same way. If using cornerstones, count those intersections separately.

Tips for beginners working with sashing

A few things that will save you frustration the first time you add sashing to a project.

• Press all sashing seams toward the sashing strip (away from the block). This makes the seams nest when you join rows.
• Measure and cut sashing strips to the exact same length. Even if your blocks are slightly different sizes, the sashing should be uniform — ease the blocks to fit.
• Use a solid or very subtle print for sashing fabric. Busy prints compete with the blocks and defeat the purpose of framing them.
• Pin the midpoint of each sashing strip to the midpoint of the block before sewing. This keeps everything centered and prevents drift.
• If you're unsure about width, make it wider rather than narrower. You can always trim, but you can't add fabric back.

Let StitchLogic handle the math

Calculating sashing yardage by hand is doable, but it gets tedious fast — especially with cornerstones and multiple fabric colors. StitchLogic's yardage calculator includes sashing as a built-in option. Choose your layout, set your sashing width, pick your cornerstone fabric, and the app calculates exact yardage for everything. No spreadsheets, no scrap paper, no second trips to the fabric store.