Quilt Border and Sashing Calculator

What the default plan means

The example grid has 4 columns × 5 rows of 12-inch finished blocks, 2-inch internal sashing and separate cornerstones. A 3-inch finished butted border, ¼-inch piecing seams, 40.5-inch net strip WOF and 2 inches of squaring per fabric are editable planning defaults.

The resulting outer unfinished top is 60.5 × 74.5 inches. For this worked example only, suppose your pattern calls for 4 yards of block fabrics, excluding the border and sashing. The separate purchases then sum to 11 ⅛ yd (11.125). The calculator leaves that pattern input blank until you supply it.

Finished sizes, raw edges and cutting formulas

For C columns and R rows of finished blocks B wide × H high, separated by finished sashing S, the finished center is C × B + (C − 1) × S wide and R × H + (R − 1) × S high. Add twice the seam allowance a to each dimension for the unfinished outer raw edges.

A sashing or border strip finishes at its entered width; cut width = finished width + 2a. With cornerstones, cut R(C − 1) vertical pieces of H + 2a, C(R − 1) horizontal pieces of B + 2a, and (C − 1)(R − 1) squares of S + 2a. Without cornerstones, the horizontal sashing runs across the whole unfinished center. No outside sashing frame is included.

For one butted border, cut the sides to the measured unfinished center height, then the top and bottom to the center width plus twice the finished border width. The outer unfinished top gains twice the finished border width in both directions.

Short equal rectangles yield floor(usable WOF ÷ cut length) pieces per WOF strip. Long pieces use enough full strips for n × WOF − 2a(n − 1) to cover one cut length, with straight joins. One unjoined strip loses no joining allowance. Fabric depth is strip count × cut width, plus the entered squaring buffer once per fabric; divide by 36 and round up to ⅛ yard. Different groups do not share offcuts.

Keep the budget complete without counting fabric twice

Enter only the block or pattern fabrics in the pattern-yardage field. This plan adds the new border, sashing and separate cornerstone fabric once. Backing uses the outer unfinished top, the selected usable backing width and per-side overhang, comparing both seam directions. Straight binding uses the existing strip-and-join model with its 12-inch working allowance. Purchases for different fabrics are rounded separately before summing; this is not a shared-bolt nesting optimizer.

For multiple rings, miters or lengthwise borders, use the existing border calculator. For individual units, use block and strip yield. Continue with backing or straight and bias binding for their detailed cutting plans.

Construction references

Quilter’s Paradise sashing reference describes crosswise strip cutting and separately subcut cornerstone squares. Its border reference distinguishes finished border width from the added seam allowance and eighth-yard purchases. The equations and conservative cutting groups shown here are this site’s own geometric model, not an imported vendor calculator.

APQS backing guidance discusses fabric width, selvages and seams; APQS machine-binding guidance covers perimeter allowance and diagonal strip joins. Actual top measurements, usable fabric width and your quilter’s margin requirements take precedence over defaults.

Questions about this plan