Border & Sashing Calculator

What is Sashing?

Sashing refers to the strips of fabric that separate individual blocks in a quilt. Sashing serves several important purposes:

• Visual separation: Creates breathing room between busy block patterns
• Size adjustment: Helps you reach a specific quilt size without making more blocks
• Design element: Adds contrasting color or frames each block
• Simplifies construction: Makes it easier to square up individual blocks

Sashing Strip Calculations

To calculate sashing fabric, you need to know your block layout (number of blocks horizontally and vertically). The calculator determines:

• Horizontal strips: These run between rows of blocks. You need one strip for each space between rows, plus strips for the top and bottom edges.
• Vertical strips: These run between columns of blocks. You need one strip for each space between columns, plus strips for the left and right edges.
• Strip length: Each strip should be the length of your finished block size plus seam allowances on both ends.

Example: For a 4×5 block layout, you need 5 horizontal sashing strips (between 5 rows) and 6 vertical strips (between 4 columns). If blocks are 10" finished, each strip should be cut at least 10.5" long (adding 0.25" seam allowance on each end).

Cornerstones

Cornerstones (also called "posts" or "sashing squares") are small squares placed at the intersections where sashing strips meet. They:

• Add visual interest and can introduce accent colors
• Simplify construction by breaking long sashing strips into smaller pieces
• Are typically the same width as your sashing strips (e.g., 2" cornerstones for 2" sashing)
• Number of cornerstones = (blocks horizontal + 1) × (blocks vertical + 1)

Choosing Your Sashing Width

Sashing width is usually described as "finished" (what you'll see once seams are sewn) rather than "cut" (the strip width before sewing, which includes seam allowance on both sides). A finished 2" sashing strip should be cut 2.5" wide with a standard 1/4" seam allowance.

• Pin or lay a scrap strip next to a finished block on a design wall before cutting your yardage — it's the fastest way to see if a width works.
• Busy or heavily pieced blocks usually read cleaner with narrower 1.5"-2" sashing, which keeps the eye from getting overwhelmed.
• Simple, large-scale blocks and modern quilt designs can carry wider 2.5"-3" sashing without looking bare.
• For a twin quilt (68"×90"), 2"-2.5" sashing is a common starting point; for a queen (92"×96"), 2.5"-3" helps the larger surface read proportionally.

Understanding Borders

Borders frame your quilt and can dramatically change its final appearance. Key considerations:

• Multiple borders: Many quilts have 2-3 borders of different widths and colors
• Border width: Common widths range from 2" to 6", with larger quilts often having wider borders
• Measuring: Always measure through the center of your quilt, not along the edges, to prevent wavy borders
• Order matters: Each border adds to the dimensions, so calculate them in the order you'll sew them

Mitered vs. Straight Corners

This calculator includes an option for mitered corners, which automatically adds extra length to account for the diagonal seams.

Fabric Cutting Tips

• Fabric direction: For borders, consider cutting lengthwise (parallel to selvage) to minimize seams. This may require more yardage but gives uninterrupted strips.
• Seam allowances: Standard quilting uses 1/4" seam allowances. The calculator includes these automatically.
• Fabric width: Most quilting cotton is 42-44" wide. Wider fabric (54-60") is less common but useful for large borders.
• Waste factor: The calculator adds a percentage for cutting mistakes, fabric shrinkage, and flaws. 10% is standard.
• Pre-washing: If you plan to wash your finished quilt, pre-wash and press your fabric before cutting to account for shrinkage.

Common Mistakes to Avoid

• Measuring along the edges instead of through the center: Quilt edges can stretch during piecing, so edge measurements often produce wavy, rippled borders.
• Forgetting seam allowance on both ends of a strip: Each sashing or border strip needs seam allowance added on both ends, not just one, or strips will come up short.
• Mismatching cornerstone and sashing width: Cornerstones cut to a different width than the sashing they join will create crooked, uneven intersections.
• Piecing border strips with a straight seam instead of a diagonal one: A straight join is far more visible in the finished quilt than a diagonal (mitered-style) seam.

Planning Your Quilt Finish

Use this calculator as part of your overall quilt planning:

1. Start with your finished block size and layout using the Block Layout Calculator
2. Determine if you want sashing and cornerstones (width and color)
3. Plan your border sequence (how many borders, widths, colors)
4. Use this calculator to determine exact fabric requirements
5. Calculate total fabric needs using the Fabric Yardage Calculator
6. Don't forget binding! Use the Binding Calculator to determine binding fabric