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.
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 uses a single fabric square or rectangle stitched into a tube, then cut in a spiral. The formula estimates the fabric needed: first it determines the side of a fabric square that yields enough bias strip area, then adjusts for the ratio of fabric width to strip width, and finally adds a waste allowance. In symbols: Fabric = ceil(√((biasLength × biasWidth × fabricWidth) / 2) / biasWidth) × fabricWidth / biasWidth × (1 + wasteAllowance / 100). The square-root term derives from the fact that a square of side S cut on the bias yields roughly S²/biasWidth inches of strip. Adding a waste percentage (typically 10–15%) accounts for joining seams and imperfect cuts.
How to use
Suppose you need 200 inches of bias tape cut at 2-inch strips from 44-inch-wide fabric, with a 10% waste allowance. Step 1 — Plug in: biasLength = 200, biasWidth = 2, fabricWidth = 44, wasteAllowance = 10. Step 2 — Inner square root: √((200 × 2 × 44) / 2) = √8800 ≈ 93.8. Step 3 — ceil(93.8 / 2) = 47. Step 4 — 47 × 44 / 2 = 1034 raw inches of fabric measurement. Step 5 — Apply waste: 1034 × 1.10 ≈ 1137 units. Use this result to purchase the right amount of fabric before cutting.
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.