About the Bias Tape Calculator
This bias tape calculator works out how much continuous bias binding you can make from a piece of fabric, or how big a square you need for a given length. Enter the fabric size and the width you will cut the strips, and it returns the total length in inches, yards and metres, plus the approximate finished width of single- or double-fold tape.
Continuous bias is made by cutting a square on the diagonal, sewing it into a tube and cutting one long spiral strip, so almost all of the fabric becomes binding. That makes the yield easy to estimate from the fabric area: area ÷ strip width. It is the method used for binding quilts with curved edges, finishing necklines and armholes, piping and making your own bias tape with a tape maker.
The result is the theoretical yield. In practice you lose a little to the two seams and to the uneven ends — allow roughly 5% less, or cut a slightly bigger square when the length really matters.
How to use the bias tape calculator
- 1Choose whether you know your fabric size or the length of bias you need.
- 2Enter the fabric dimensions, or the length of tape required in inches.
- 3Enter the strip width you will cut (2" makes 1/2" double-fold tape).
- 4Read the bias length or square size, then cut slightly larger for seam losses.
Formula and method
When you cut continuous bias, the whole piece of fabric is turned into one long strip of width w, so the strip length is the fabric area divided by the strip width. A 36" square has 1,296 sq in of fabric; cut into 2" strips that is 648", or 18 yards. The same rule works for rectangles.
Reversing it, the square needed for a given length is the square root of length × strip width. Double-fold bias tape finishes at about one quarter of the cut width (the edges fold to the centre and then it folds in half), and single-fold at about half. Real yields are a few percent lower because of the two seams and the angled ends.
- W, L
- Fabric width and length (inches)
- w
- Cut strip width (inches)
Worked examples
36" square, 2" strips
A 36" square holds 36 × 36 = 1,296 sq in of fabric. Divided by the 2" strip width that is 648" of continuous bias — exactly 18 yards — which folds into 1/2" wide double-fold tape.
Fat quarter (18" × 22"), 1 1/2" strips
A fat quarter is 18 × 22 = 396 sq in. Cut into 1.5" strips it yields 396 ÷ 1.5 = 264" (about 7 1/3 yards) of bias, which presses into single-fold tape about 3/4" wide.
Square needed for 250" of 2 1/2" binding
You need 250 × 2.5 = 625 sq in of fabric, and √625 = 25, so a 25" square makes 250" (about 6.9 yards) of 2 1/2" bias binding. Cut 26" or so to allow for seam losses.
Frequently asked questions
How much bias tape does a yard of fabric make?+
A 36" square cut from one yard of fabric makes about 648" (18 yards) of 2" bias strips, or 864" (24 yards) of 1 1/2" strips. Using the full 42" width gives proportionally more.
What width should I cut bias strips?+
Cut strips four times the finished width for double-fold tape — 2" for 1/2" tape — and twice the finished width for single-fold. For double-fold quilt binding on curves, 2 1/4" to 2 1/2" strips are common.
How do I make continuous bias binding?+
Cut a square in half diagonally, sew the two triangles into a parallelogram, mark lines one strip-width apart, then sew the ends into an offset tube and cut along the lines in one long spiral.
Why is my bias tape shorter than the calculator says?+
The formula assumes every square inch becomes tape. The seams, the pointed ends and any trimming typically cost a few percent, so allow about 5% extra fabric when the length matters.
Do I need bias binding for a quilt?+
Only for curved or scalloped edges, or when you want a plaid or stripe to run diagonally. Quilts with straight edges can use straight-grain binding, which uses less fabric and is quicker to cut.