Bias Tape Calculator — Fabric Square Size & Yield

Bias tape is a general term for a strip of fabric cut at 45 degrees to the grain line. Bias binding specifically refers to tape used to finish raw edges. Both use the same cutting method — the terms are often used interchangeably in UK sewing. This calculator works for both purposes.

For single-fold tape, cut strips at twice the desired finished width (e.g., a 12mm finished tape needs 24mm = 2.4cm strips). For double-fold tape, cut at four times the finished width (a 12mm finished tape needs 48mm = 4.8cm strips, which then fold to a finished 12mm). These 2× and 4× ratios match every standard bias-tape-maker tool. This calculator works out the cut width from your finished width and fold type automatically.

Rather than cutting individual diagonal strips and joining them by hand, you mark parallel diagonal lines across a fabric square, join two opposite edges with an offset of one strip width, and cut in a spiral. The result is one long continuous strip with minimal hand-sewing of joins. It is the most efficient method for making bias tape in quantity.

Always build in at least 10% extra for the loss at the start and end of the spiral cut, plus any joins needed for seaming strips together. For small quantities (under 1 metre), allow 15–20% extra as the proportional waste is higher. The waste buffer in Advanced Options adjusts this for you.

Most woven fabrics work well — cotton lawn and quilting cotton are popular for lightweight tape, while dressmaking cotton suits garment use. Avoid very heavy fabrics as the multiple layers at fold points become bulky. Pre-washing is advisable to prevent finished tape from shrinking after application.