Bias Tape Calculator
Find exactly how much fabric you need to cut continuous bias tape or binding for quilts, garments, and crafts. Enter your desired tape length, strip width, and fabric width to get precise yardage.
Last updated: May 2026
About this calculator
Bias tape is cut diagonally across the fabric grain at 45°, which gives it the stretch needed to curve around edges. The continuous bias method seams a single fabric rectangle into a tube and cuts it in one long spiral, which is why the maths reduces to simple area conservation: the standard continuous-bias yield formula states that a piece of fabric yields a total strip length equal to its area divided by the strip's cut width (binding inches = fabric area ÷ cut width). Turning that around, the fabric area you must buy is the bias length you need times the cut width of the strip. This calculator computes that area, multiplies by a waste factor for the diagonal joining seams and squared-off corners, then divides by the bolt's fabric width to get the length of fabric to buy, converting inches to yards: yards = (biasLength × biasWidth × wasteAllowance) ÷ fabricWidth ÷ 36. The 45° bias angle does not change the area required — it only sets the direction of the cut — so no trigonometric term appears. A waste allowance of 10–20% covers the joining seams and the triangular offcuts at the start and end of the spiral.
How to use
Suppose you need 200 inches of continuous bias binding cut at 2¼-inch strips from 44-inch-wide quilting cotton, with a 10% waste allowance. Enter biasLength = 200, select biasWidth = 2.25 (2¼ inch, for ½ inch binding), enter fabricWidth = 44 and select wasteAllowance = 1.1 (10% extra). Step 1 — fabric area needed: 200 × 2.25 = 450 sq in of strip, × 1.1 waste = 495 sq in. Step 2 — length off a 44-inch bolt: 495 ÷ 44 = 11.25 inches. Step 3 — convert to yards: 11.25 ÷ 36 = 0.31 yards. So a fat quarter easily covers it. Cutting wider 2½-inch strips for the same 200 inches (biasWidth = 2.5) at 20% waste raises it to 200 × 2.5 × 1.2 ÷ 44 ÷ 36 = 0.38 yards — wider tape simply eats proportionally more fabric.
Frequently asked questions
What is continuous bias tape and why is it cut on the bias?
Continuous bias tape is a long strip of fabric cut diagonally at 45° to the grain, then joined into one seamless length using the continuous tube method. The diagonal cut gives the tape natural stretch and flexibility, allowing it to ease around curves, necklines, and quilt edges without puckering. This makes it far more versatile than straight-grain binding for curved or circular applications. The continuous method also reduces waste compared to cutting many individual strips.
How much waste allowance should I add when calculating bias tape fabric?
A waste allowance of 10–15% is standard for most bias tape projects to account for the diagonal joining seam, thread tails, and any cutting errors. For very precise or intricate work, bump this up to 20%. If you are a beginner or working with slippery fabric like silk, using 20% gives you a comfortable buffer. It is always better to buy a little more fabric than to fall short mid-project.
How do I choose the correct cut width for bias strips?
The cut width of your bias strip depends on the finished tape width you need and whether the tape will be folded once or twice. For double-fold bias tape with a finished width of ½ inch, cut strips at 2 inches wide. For single-fold tape finishing at ½ inch, cut at 1¼ inches. Always account for two seam allowances (typically ¼ inch each side) when calculating cut width from finished width. Test a small sample first to confirm your iron folds produce the desired result.