Bias Binding Calculator
Find out how big a square of fabric you need to cut continuous bias strips for curved edges or scrappy binding.
Tip: use URL parameters, e.g. ?quiltWidth=60&quiltLength=80&bindingWidth=2.25.
How the bias binding calculation works
Bias binding is cut at 45° to the grain, which gives the fabric stretch — essential for binding curved edges. The neat trick is that you can cut one long continuous strip from a single square of fabric by sewing the square into a tube and spiraling around it.
Step 1: find the binding length. Same as straight binding: perimeter plus a joining allowance. A 60" × 80" quilt needs about 292 inches.
Step 2: calculate the fabric area. The strip has length × width of area. Multiply the binding length by the cut strip width: 292 × 2.25 = 657 square inches.
Step 3: convert to a square. Take the square root of the area: √657 ≈ 26 inches. Add a couple of inches for seam allowance and errors, and you have your starting square size.
For example, a 28" square of fabric yields roughly 300+ inches of 2.25" bias binding. If you don't have a square big enough, you can cut bias strips from two smaller squares and join them.
What each input means
- Quilt width and length (inches) — the outer dimensions of the quilt you're binding. The calculator uses them to find the perimeter, which is the minimum length of binding you need.
- Binding width (cut width, inches) — how wide you cut each bias strip before folding. Standard is 2.25" to 2.5" for a finished binding around 3/8" to 1/2".
The calculator doesn't ask for fabric width because the continuous-bias method works from a square: the fabric width determines how many strips you can cut around the tube, but the total length is set by the square's area and your strip width.
When to use it. Reach for this calculator on any project with curved or scalloped edges — baby quilts with scalloped borders, table runners with rounded ends, or quilts with appliquéd curves. If your quilt is a plain rectangle, straight-grain binding is the cheaper, simpler choice; this calculator is for the projects where the fabric's diagonal stretch actually matters.
Common mistakes to avoid
- Cutting the square to the exact calculated area. The seams that join the tube and the diagonal joints each consume fabric. Adding 2–3 inches to the side is standard practice.
- Forgetting the perimeter allowance. Like straight binding, you need a little extra length beyond the perimeter for joining and folding at corners.
- Using bias binding where straight binding works. Bias uses more fabric for the same job; save it for curved or scalloped edges where the stretch matters.
- Sewing the tube seams too wide. A wider seam eats into the strip width and shortens your binding — use a scant 1/4" and check your seam allowance before cutting.
- Assuming one square is the only option. If your fabric is a fat quarter or half-yard, cut bias strips from a rectangle and join them on the diagonal instead of forcing a square.
Frequently asked questions
When should I use bias binding instead of straight binding?
Use bias binding for curved or scalloped edges — the diagonal grain stretches to follow curves without puckering. For straight edges, straight binding is simpler and uses less fabric.
How do I cut continuous bias strips?
Sew the square into a tube (offset the seams by one strip width), then cut around in a spiral. Many video tutorials show the method; it takes one practice run to get the hang of it.
What width should bias binding strips be cut?
The same as straight binding: 2.25" to 2.5" cut width gives a finished binding of about 3/8" to 1/2".
Why is my bias binding not long enough?
Check your seam allowances when joining the tube — each seam consumes fabric. Cutting the starting square 2" larger than calculated gives comfortable margin.