Quilt Border Calculator
Work out how much fabric you need for one or multiple borders, including mitered corners.
Tip: use URL parameters, e.g. ?quiltWidth=50&quiltLength=60&borderWidth=4.
How the border calculation works
Borders frame your quilt and give the eye a place to rest. The fabric math starts with the outer perimeter: after one border, the quilt grows by twice the border width in each direction, so each additional border needs a little more length.
Step 1: find the outer size. For each border, the quilt grows by 2 × border width. One 4" border on a 50" × 60" top makes the finished outer size 58" × 68".
Step 2: calculate the outer perimeter. 2 × (58 + 68) = 252 inches for the outer edge of the first border. Add a joining allowance of about 12 inches, then divide by your usable fabric width and round up to get the number of border strips.
Step 3: convert to yardage. Multiply the strips by the cut border width (finished width plus seam allowances) and divide by 36.
This calculator treats each border separately and adds its length to the quilt size, then sums the yardage. Mitered corners need a little extra at each corner — the joining allowance covers it for most quilts.
What each input means
- Quilt top width and length (inches) — the size of your pieced top before any borders. Include sashing if you've added it, and measure a straight average if your top isn't perfectly square.
- Border width (finished, inches) — the width the border will show after quilting. The strips you cut are 0.5" wider to allow for the 1/4" seams on each side.
- Number of borders — how many borders you're stacking. Each one wraps around the quilt made larger by the previous border, so the calculator grows the dimensions as it goes.
- Fabric width (usable) — the cutting width after selvedges, about 42" for standard 44"–45" quilting cotton.
When to use it. Use this calculator whenever you add one or more borders to a quilt top, whether it's a simple single frame or a stacked multi-border treatment. It's especially handy for bed quilts where you're adjusting to reach a target mattress size: change the border width and count and watch how the finished outer size and yardage move together, so you can compare design options before you buy fabric.
Common mistakes to avoid
- Cutting at the finished width. A 4" finished border needs 4.5" cut strips; forget the seam allowance and you'll lose 1/2" overall.
- Measuring only one side. The border runs around the whole quilt, so it's two widths plus two lengths (plus corners), not a single edge.
- Forgetting that borders change the quilt size. Your second border starts from the enlarged quilt, and this calculator handles the growth for you.
- Skipping the miter allowance. If you miter the corners, each corner consumes a little extra length — the built-in 12" allowance covers typical quilts.
- Piecing borders where seams will show. Plan strip joins so they're balanced or centered rather than at obvious spots, and press seams carefully.
Frequently asked questions
How wide should quilt borders be?
Four to six inches is common for a single border on a lap or bed quilt. Wide quilts can handle 6-8" borders; small wall hangings look better with 2-3".
Do I need to miter border corners?
No — butt joints are simpler and perfectly fine for most quilts. Mitered corners look more formal but add a little length to the math, which this calculator's allowance covers.
Should I cut border strips along the grain?
Cutting along the lengthwise grain keeps long borders from stretching, but most quilters use width-of-fabric strips pieced together. It's a practical tradeoff.
Why does a second border need more fabric than the first?
Each border increases the quilt's outer size, so the next border's perimeter is longer. The calculator accounts for this automatically.