Quilt border calculator
Start from the top as it measures now, add up to three borders, and choose butt or mitered corners. The calculator returns the cut size of every strip, the quilt size after each border lands, and the yardage per fabric, with all borders in one fabric or a fabric each.
Cutting plan: All borders, one fabric
Bolt view: 42 in usable wide by 36 in long, drawn to scale. Shaded bands are leftover inside the purchased length: 0 sq in (0.00 sq ft). Dashed outlines are segmented strips that get joined end to end.
- Cut a 4 4/8 in strip: Border 1 side strip (segment 1 of 2)
- Cut a 4 4/8 in strip: Border 1 side strip (segment 2 of 2)
- Cut a 4 4/8 in strip: Border 1 side strip (segment 1 of 2)
- Cut a 4 4/8 in strip: Border 1 side strip (segment 2 of 2)
- Cut a 4 4/8 in strip: Border 1 top/bottom strip (segment 1 of 2)
- Cut a 4 4/8 in strip: Border 1 top/bottom strip (segment 2 of 2)
- Cut a 4 4/8 in strip: Border 1 top/bottom strip (segment 1 of 2)
- Cut a 4 4/8 in strip: Border 1 top/bottom strip (segment 2 of 2)
The formula, in words
The cut width of a border is its finished width plus 1/2 in of seam allowance. With butt joints, the side strips are cut to the current length plus seam allowance, and the top and bottom strips span the width including the side borders already sewn, plus seam allowance. With mitered corners, every strip is cut to span the full side including both border widths, plus a 1 in spare for the miter fold. After each border, the quilt grows by twice the finished width in both directions, and the next border is measured from the new size.
Worked example
A 40 x 60 in top with one 4 in border, butt joints: the border cuts at 4.5 in wide. The two side strips are 4.5 x 60.5 in, and the top and bottom strips are 4.5 x 48.5 in, because they span the 40 in width plus the two 4 in side borders, plus seam allowance. The quilt finishes at 48 x 68 in.
Questions quilters ask
Butt joints or mitered corners?
Butt joints are the standard: easier to sew, easier to keep square, and the seam lines read as a clean frame corner. Mitered corners continue prints and stripes around the corner and look tailored, but they need the extra length and careful 45 degree sewing. The calculator prices both.
Why are the top and bottom strips longer than the quilt is wide?
Because they are sewn after the side borders and span across them. A top strip covers the quilt width plus both side border widths, plus a seam allowance. Measuring it to the bare quilt width is the classic border mistake and leaves it 8 in short on a 4 in border.
Can the borders be different fabrics?
Yes. Keep the one-fabric plan and the strips pack together on a single bolt, or switch to a fabric per border and each border gets its own yardage and cutting plan.
How wide should a border be?
Proportion rules of thumb: a single border at about a sixth of the quilt's shorter side reads balanced, and multiple borders usually step up in width, narrow inside and wider outside. The calculator takes whatever widths you give it, up to three borders.