Bias Tape Yardage Calculator
Find the strip width and size of the fabric square needed to make continuous bias tape of any length.
How it works
Strip width = finished × 2 (single-fold) or × 4 (double-fold) · Fabric area = length × strip width · Square side = ⌈√area⌉
Bias tape is cut at 45 degrees so it stretches around curves without puckering. The continuous-bias method sews one fabric square into a tube and cuts a spiral, turning a small square into yards of unbroken strip. The area of tape you need equals its length times its cut width, so the side of the fabric square you start from is just the square root of that area — plus a little rounding up for the diagonal join.
Worked example
You need 120 in of half-inch double-fold tape. Double-fold cuts at 4 × 0.5 = 2 in wide, so the fabric consumed is 120 × 2 = 240 sq in. The square root of 240 is about 15.5, so a 16 in square of fabric makes the whole length continuously.
Frequently asked questions
What is the difference between single- and double-fold bias tape?
Single-fold has both raw edges pressed to the center and is cut at twice the finished width — good for facings and casings. Double-fold folds that in half again to encase a raw edge, so it is cut at four times the finished width and shows on both sides.
Why cut on the bias at all?
The true bias, at 45 degrees to the grain, has the most stretch, letting the tape curve smoothly around necklines, armholes and scalloped edges. Straight-grain strips would ripple or pull on a curve.
How accurate is the square-size estimate?
It is a close area-based approximation. The continuous-bias tube wastes a little at the diagonal seam and the ends, so rounding the square up by an inch or two, as this does, keeps you from coming up short.
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This calculator is for educational purposes. Double-check important results before acting on them.