Quilt Sashing Calculator: Sashing Strips for a Block Layout

How the calculator works

Step 1: Finished quilt size

Finished quilt width equals blocks across times block finished size, plus blocks across minus 1 times sashing finished width, because sashing strips sit between blocks, not around the outside, and there is one fewer sashing strip than blocks in each row. For blocks across 5, block finished size 12 inches, sashing finished width 2 inches, finished quilt width equals 5 times 12, which is 60, plus 4 times 2, which is 8, which is 68 inches. Finished quilt length equals blocks down times block finished size, plus blocks down minus 1 times sashing finished width. For blocks down 6, block finished size 12 inches, sashing finished width 2 inches, finished quilt length equals 6 times 12, which is 72, plus 5 times 2, which is 10, which is 82 inches.

Step 2: Vertical sashing strips

This calculator uses continuous vertical sashing strips and no cornerstones. Vertical sashing strips needed equals blocks across minus 1, each running the full finished quilt length. For blocks across 5, vertical sashing strips needed equals 4 strips. Cut width for each vertical strip equals sashing finished width plus 0.5 inch, for seam allowance 0.25 inch on each side, which is 2.5 inches. Cut length for each vertical strip equals finished quilt length plus 0.5 inch, for seam allowance 0.25 inch on each end, which is 82.5 inches.

Step 3: Horizontal sashing segments

Horizontal sashing segments needed equals blocks down minus 1 times blocks across, because each horizontal segment runs between two vertical strips, and each row of sashing between block rows is cut into one segment per block. For blocks down 6 and blocks across 5, horizontal sashing segments needed equals 5 times 5, which is 25 segments. Cut width for each horizontal segment equals sashing finished width plus 0.5 inch, which is 2.5 inches. Cut length for each horizontal segment equals block finished size plus 0.5 inch, for seam allowance 0.25 inch on each end, which is 12.5 inches.

Step 4: Total sashing pieces and total sashing length

Total sashing pieces equals vertical sashing strips plus horizontal sashing segments. For vertical strips 4 and horizontal segments 25, total sashing pieces equals 29 pieces. Total sashing length, cut, equals vertical strips times vertical cut length, plus horizontal segments times horizontal cut length. For vertical strips 4 times 82.5 inches, which is 330 inches, plus horizontal segments 25 times 12.5 inches, which is 312.5 inches, total sashing length, cut, equals 642.5 inches.

Assumptions, shown next to the result

This calculator assumes square blocks only, sashing between blocks only, with no sashing around the outside of the quilt top, and no cornerstones, with continuous vertical sashing strips. If you want sashing around the outside, use the Border Calculator for that outer frame, after sashing is worked out. If you want cornerstones, the layout is different, because horizontal sashing strips run full width and cornerstones sit where vertical and horizontal sashing strips cross, so do not use these strip counts for a cornerstone layout. Sashing finished width must be greater than zero, and block finished size must be greater than zero. This calculator gives strip counts, cut sizes and total sashing length, not fabric yardage, because yardage depends on fabric width and cutting layout. Use the Strip Calculator with total sashing length, or the Fabric Calculator, for yardage from total sashing length.

Sashing layout chart

This chart uses the same formulas as the calculator, with block finished size 12 inches and sashing finished width 2 inches, with continuous vertical sashing strips and no cornerstones.

Chart values are a guide for the layouts shown. Your own layout, block size or sashing width may give a different result. Use the calculator above for your own measurements.

Worked example, checked against the calculator

Blocks across 5, blocks down 6, block finished size 12 inches, sashing finished width 2 inches.

Finished quilt width: 5 times 12 equals 60, plus 4 times 2 equals 8, which is 68 inches. Finished quilt length: 6 times 12 equals 72, plus 5 times 2 equals 10, which is 82 inches.

Vertical sashing strips: 5 minus 1 equals 4 strips, each cut 2.5 by 82.5 inches.

Horizontal sashing segments: 6 minus 1 times 5 equals 25 segments, each cut 2.5 by 12.5 inches.

Total sashing pieces: 4 plus 25 equals 29 pieces. Total sashing length, cut: 4 times 82.5 equals 330, plus 25 times 12.5 equals 312.5, which is 642.5 inches.

Frequently asked questions

Related calculators

Guide for this topic: How to Calculate Sashing.