Bias Tape Calculator
Calculate the fabric square needed to make continuous bias tape, or how many purchased packages to buy.
Common Bias Tape Uses
| Application | Common Tape Width | Type |
|---|---|---|
| Quilt binding | 2½" strips (makes 1¼" binding) | Double-fold |
| Garment neckline / armhole | 1" strip (½" finished) | Double-fold or single-fold |
| Appliqué outline | ½" strip | Single-fold |
| Bag / tote edge | 2" strip | Double-fold |
| Facing alternative | 1–2" strip | Single-fold |
| Piping casing | Varies by cord size | Bias-cut strip |
How to Use the Bias Tape Calculator
- Measure all the edges you need to bind and add them together for the total tape length needed (in inches).
- Select the strip width — for double-fold bias tape, the standard is 2" wide strips folded to 1" finished.
- Choose your joining seam allowance (¼" is standard for bias tape joins).
- Select a safety buffer to account for waste and errors.
- Click Calculate to see the fabric square size needed and how many purchased packages to buy.
How Continuous Bias Tape Works
- Cut a square of fabric. The size of the square determines how much tape you get.
- Cut the square in half diagonally to make two triangles.
- Sew the triangles together along the short straight edge (¼" seam) to make a parallelogram.
- Draw parallel lines across the fabric at the desired strip width.
- Join the top and bottom edges with a ¼" offset to make a tube. Sew together.
- Cut along the spiral lines to produce one continuous bias strip.
Formula Used
- The area of the fabric square (side²) divided by the strip width gives the theoretical tape length.
- A small amount is lost to seam allowances when joining; the calculator accounts for this.
- For a 20" square cut into 2" strips: 20" × 20" ÷ 2" = 200" of tape (theoretical).
Tips
- Cut strips on the true bias (45° to the grain) for maximum stretch and smooth curves.
- Pre-cut quilting strips are not bias — they are cut straight and do not stretch around curves.
- Use a bias tape maker tool to fold and press strips quickly and evenly.
About this Bias Tape Calculator
This works backward from how much bound edge you need to the size of fabric square to cut, using the continuous bias method — cut a square, seam it into a tube on the bias, then spiral-cut one long strip. It assumes true bias-cut fabric (strips at 45° to the grain), since that's what gives bias tape its stretch around curves; straight-grain strips of the same width don't behave the same way and won't ease around curves smoothly.
Why the safety buffer matters
The continuous method always loses a little length to the diagonal seam that joins the tube into a spiral, which is why the calculator adds about 8% to the fabric area before finding the square size. Cutting exactly to that number with no further buffer is a common way to come up short partway through binding a project — the 15% option covers ordinary cutting and piecing waste on top of the seam loss. For the joining seam itself, see the Seam Allowance Calculator.