Calculator
Mitered Border Calculator
How much fabric for a mitered (45°-corner) border. Strip lengths and yardage for a 4″ border by quilt size, plus the formula for any width.
4″ Mitered Border Yardage by Quilt Size
| Quilt Size | Yards |
|---|---|
| Baby / Crib | 0-3/4 yds |
| Throw / Lap | 1 yds |
| Twin | 1-1/4 yds |
| Full / Double | 1-3/8 yds |
| Queen | 1-1/2 yds |
| King | 1-5/8 yds |
Assumes a 4″-finished border, strips cut 4.5″ wide, pieced from width-of-fabric (44″) strips with 6″ trimming margin per strip. For a seamless (unpieced) border, cut lengthwise along the yardage instead — buy yardage equal to your longest strip length.
The Formula for Any Border Width
- 1. Strip length: quilt top's side length + (2 × border width) + 6″ trimming margin. Do this for both the width and the height.
- 2. Cut width: border width + 1/2″ seam allowance.
- 3. Total length needed: 2 × (width-direction strip length) + 2 × (height-direction strip length).
- 4. Strips from width-of-fabric: total length ÷ 40″ (usable WOF), rounded up.
- 5. Yardage: (number of strips × cut width) ÷ 36.
Shop Border Fabric
Striped and border-print fabrics show off a mitered corner best — solids work too.
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Frequently Asked Questions
How much fabric do I need for a mitered border on a queen quilt?
For a queen quilt (90×108") with a 4"-finished mitered border, you need about 1-1/2 yards: two strips cut 104" long and two strips cut 122" long, each 4.5" wide (4" finished + 1/2" seam allowance), pieced from 12 width-of-fabric strips.
How do I calculate strip length for a mitered border?
Strip length = the quilt top's side length + 2 × border width + about 6" extra for the 45° miter and trimming margin. Cut two strips at this length for each pair of opposite sides. Always cut border strips longer than you think you need — trimming off extra is easy, running short is not.
How do I sew a mitered corner?
Center each border strip on its side and sew, stopping and backstitching 1/4" from each corner (don't sew into the seam allowance). Fold the quilt diagonally at the corner, right sides together, and draw a 45° line from the inner corner to the outer edge through both border strips. Sew on the line, check it lies flat, then trim the seam allowance to 1/4" and press open.
Why use a mitered border instead of a straight (butted) border?
A mitered border creates a continuous, uninterrupted line at each corner — especially important for striped, directional, or border-print fabrics, where a straight butted corner would create a visible seam mismatch. It uses slightly more fabric (extra length + the miter's trimming margin) than a butted border of the same width.