Bias Tape Calculator

What this calculator does

Continuous bias tape is made by cutting a fabric square, slicing off one corner triangle, and sewing the piece into a tube marked with diagonal lines. When you cut along those lines you get one long, unbroken bias strip. This tool tells you how much tape a square yields — and how big a square you need for a job — using the standard sewing formula:

total bias length = (side × side) ÷ strip width

All three numbers must be in the same unit. If your square side and strip width are in inches, the length comes out in inches (we also show yards). Pick centimeters and you get centimeters and meters. Results are estimates — real yield drops slightly for seam allowances and the trimmed starting/ending tips.

Why the square-and-tube method

Cutting many short bias strips and joining them wastes fabric and leaves lumpy seams. The continuous-tube method turns one square into yards of tape with only two seams total, so it is the go-to for quilt binding, piping, and Hong Kong seam finishes.

How to use it

1. Choose your units (inches or centimeters).
2. Leave it on Square → Bias length to see how much tape a square makes, or switch to Target length → Square to size a square for a project.
3. Enter your fabric square size (one side) or your target length.
4. Enter the strip width — the full cut width of each bias strip, before folding.
5. Read the result, then add roughly 5–10% extra for seams and trimmed tips.

FAQ

What strip width should I use?

For double-fold tape, the cut strip is about four times the finished folded width. A 1/2 inch finished binding needs a 2 inch strip.

Is the strip width the finished tape width?

No — enter the cut width of the flat strip. The formula divides fabric area by that cut width.

How much fabric should I buy?

Use the reverse mode to get the square side, then buy fabric at least that wide and long, plus a little margin.

Does my data leave my computer?

No. Every calculation runs in your browser — nothing is uploaded or saved anywhere.