How it works
Cut width = finished width + ½"
Butted: sides = top length, top & bottom = top width + 2 × border
Mitered: each strip = its side + 2 × border + extra
WOF strips = round up( (total − ½") ÷ (usable − ½") )
Yardage = strips × cut width ÷ 36, rounded up to ⅛ yd
Every border strip is cut 1/2" wider than its finished width, which covers a 1/4" seam on each long edge. A 4" border is cut 4 1/2" wide.
For butted corners, the side borders go on first. Cut them to the length of the quilt top, measured through the middle rather than along the edges, because edges stretch. Then measure the width again, now including the side borders, and cut the top and bottom strips to that length. Each finished border adds twice its width to both dimensions. With more than one border, you repeat the process on the bigger top, so the calculator measures border 2 on a quilt that already has border 1.
Mitered strips need more length. Each strip is the side it goes on, plus two border widths for the diagonal at each end, plus a few inches of spare (3" by default) so you can line up the miter.
Cut across the fabric, strips are sewn end to end, and each join uses 1/2". The calculator adds up all four strips and works out how many width-of-fabric strips cover that length. Cut along the length, there are no joins: you buy the longest strip, and the strips sit side by side across the fabric.
Yardage is rounded up to the nearest 1/8 yard.
Worked example
A 60" x 72" top with a 2" inner border and a 5" outer border, butted, with 40" of usable fabric. Border 1 is cut 2 1/2" wide: two sides at 72" and a top and bottom at 64". That is 272" in all, so 7 strips and 1/2 yd. The top is now 64" x 76". Border 2 is cut 5 1/2" wide: sides 76", top and bottom 74", 8 strips, 1 1/4 yd. The finished top is 74" x 86". Mitered with 3" spare, the same borders need 5/8 yd and 1 3/8 yd.
Common mistakes
- Cutting borders to the length of the quilt edge. Edges stretch, so measure through the middle and ease the quilt to fit the border, not the other way round.
- Forgetting that the second border is longer. Each border is measured on the quilt with the previous border already sewn on.
- Cutting mitered strips to the butted length. A miter needs two extra border widths plus some spare on every strip.
- Joining border strips with diagonal seams and not buying extra. A diagonal join uses more fabric than the 1/2" allowed here, so add a strip if you join on the bias.
Last checked October 2026 against standard quilting and knitting math. Found a mistake? Tell us and we’ll fix it.