Bias Tape Length Calculator
Calculate how much bias tape or binding you need to finish the edges of a fabric project, including extra for mitering corners and a working buffer. Use it whenever you are binding a quilt, neckline, armhole, or finishing the edge of any cut piece.
Last updated: May 2026
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About this calculator
The formula is: biasTapeNeeded = perimeterLength + (corners × 2) + extraAllowance, where perimeterLength is the total edge to bind (in inches), corners is the number of mitered corners requiring extra tape, and extraAllowance is a working buffer for joining the ends and securing the finish. Each corner consumes approximately 2 inches of additional tape because the miter folds back over itself diagonally to create the corner finish without bulk. A typical quilt has 4 corners; a triangular shape has 3 corners; a circular shape has zero corners but requires the same 4–6 inches of extra for the joining seam where the binding meets itself. Standard extra allowance: 6–10 inches for most projects, covering the final join overlap (3 inches), one mistake, and the inherent stretch of bias tape when sewn around curves. Bias tape (also called "bias binding") is fabric strips cut at 45° to the fabric grain, giving the strips natural stretch and the ability to curve smoothly around curved edges (necklines, armholes, scallops). Straight-grain binding does not curve; only bias-cut binding follows curved edges cleanly. Widths: 1/2 inch single-fold (most common for finishing seams internally); 1 inch double-fold (for quilt binding, most common); 2 inch double-fold for thicker quilts and wide finish. Each width has standard packaged sizes (1/4 inch single, 1/2 inch single, 1/2 inch double, 7/8 inch double) sold at fabric stores. To estimate yardage from perimeter inches: divide by 36 for yards. For continuous bias binding made from a single fabric square, the calculation differs slightly (45° strips connected) and is usually presented as a yards-from-square-size table rather than perimeter math.
How to use
Example 1 — Standard quilt binding. 60 × 80 inch quilt, 4 corners, 8 inches extra. Perimeter = 2 × (60 + 80) = 280 inches. Enter perimeterLength 280, corners 4, extraAllowance 8. Result: 280 + (4 × 2) + 8 = 296 inches ≈ 8.2 yards of binding. ✓ Most quilters buy or make 9 yards to allow for the joining and any minor mistakes. For 2.5-inch-wide strips cut from yardage (the standard for double-fold quilt binding), you need roughly 1 yard of binding fabric per 11 linear yards of finished binding (with cutting efficiency); for 9 yards of binding, buy 1 yard of fabric. Example 2 — Round placemat binding. Single circular placemat 18 inches diameter, 0 corners (continuous curve), 6 inches extra. Perimeter (circumference) = π × 18 ≈ 56.5 inches. Enter perimeterLength 56.5, corners 0, extraAllowance 6. Result: 56.5 + 0 + 6 = 62.5 inches ≈ 1.75 yards. ✓ Round to 2 yards. For curved bindings, bias tape (cut at 45°) is essential — straight-grain tape will buckle on curves. Pre-fold the tape using a bias-tape maker tool or iron the fold along the centerline before applying.
Frequently asked questions
What is bias tape and why is it cut on the bias?
Bias tape is a long narrow strip of fabric cut at 45 degrees to the warp and weft of the original fabric (the "bias" direction). Fabric cut on the bias has natural stretch — pulling along the bias allows the strip to elongate and curve smoothly, unlike straight-grain strips which resist curving and buckle or pucker. This makes bias tape essential for binding curved edges (necklines, armholes, scalloped hems, round corners) and for creating smooth piping. Bias tape is sold pre-folded in standard widths (1/4, 1/2, 7/8, 1 inch) or made from your own fabric using a bias-tape maker tool. Common forms: single-fold (one fold along the center, used for finishing internal seam edges); double-fold (folded again so both raw edges meet in the center, then folded down the middle — used for visible binding on quilts, garments, placemats); single-fold can become double-fold by ironing a second fold. Each fold is critical for the finished application; mismatched fold use creates ugly or unprofessional finishes.
How do I calculate continuous bias binding from a fabric square?
Continuous bias is a clever method that produces a long binding strip from a single square of fabric without joining many short strips. The math: a square with side S can produce roughly (S × S) / (binding width × 1.05) inches of continuous bias binding. Examples: a 12-inch square produces ~144 / 2.5 ≈ 57 inches of 2.5-inch-wide binding (suitable for a placemat). An 18-inch square produces ~324 / 2.5 ≈ 130 inches. A 22-inch square produces ~480 / 2.5 ≈ 192 inches (about 5 yards) — enough for a small quilt. A 27-inch square produces ~729 / 2.5 ≈ 290 inches (about 8 yards) — full-size quilt. The method: mark the square diagonally (45° line), sew the top edge to the bottom edge offset by one strip width, then cut around the resulting tube in a spiral to produce a long single strip. Bonnie Hunter, Jenny Doan, and others have tutorial videos showing the exact construction. For consistent results, use a fabric weight similar to the quilt itself; lighter fabric stretches more and produces uneven binding.
What width of bias tape should I use?
Depends on the application. Quilt binding (most common): 2.5 inches wide cut, folded into 1/2-inch double-fold finish — the universal modern quilting standard. Garment binding for visible finish (sleeves, necklines, plackets): 7/8 inch double-fold or 1/2 inch single-fold are common. Internal seam-finishing (Hong Kong finish on inside seams): 1/2 inch single-fold; the binding is sewn over the seam allowance and tucks inside. Piping: 1 to 1.5 inches wide cut, folded around piping cord. Bias facings (replacing standard interfaced facings with a flat bias finish): 1.5 to 2 inches wide. Trim and decoration: 1/4 to 1/2 inch single-fold. For commercial pre-made bias tape, the package marks indicate finished width when fully extended (1/4 inch means the visible binding is 1/4 inch wide when sewn). Match width to the project's scale — large quilts need wider binding (1/2 inch) than small quilted potholders (1/4 inch).
What are the most common bias tape mistakes?
The biggest is using straight-grain tape on curves; it puckers and refuses to lie flat. Always cut at 45° for any curved edge. The second is making too little binding and running short during construction; buy or make 10–20% extra. The third is sewing binding while it is stretched; bias tape can elongate 10–20% under tension, and binding sewn stretched will buckle when relaxed. Keep the binding relaxed as you sew — feed it through without pulling. The fourth is uneven binding width caused by inconsistent seam allowance; use a quarter-inch foot or a seam guide to maintain consistent stitch placement. The fifth is mitering corners incorrectly, producing bulky or twisted corners; the standard miter fold method (stop 1/4 inch from corner, fold binding away, fold back over to next side) takes practice but yields professional results. The sixth is joining binding ends with a butt seam (overlapped and stitched) instead of a diagonal seam; diagonal joins distribute bulk and lie flatter. The seventh is choosing a binding fabric that bleeds in the first wash; pre-wash binding fabric especially for quilts. The eighth is using a fabric with too much directional pattern (large plaids, stripes) cut on the bias; the pattern becomes diagonal in the finished binding, which is sometimes desired and sometimes a surprise.
When should I not use this calculator?
Skip it for non-bias binding (straight-grain binding on straight-edge projects like rectangular placemats); the formula still works but bias-specific calculations may differ slightly. It is the wrong tool for piping calculations where the cord-around-fabric layer adds bulk; piping is typically wider cut than binding to wrap the cord. Do not use it for projects with many small intricate shapes (binding around appliqued pieces, scalloped edges with dozens of curves) where the perimeter is hard to estimate and the extra allowance should be much more generous than 6–10 inches. For Hong Kong seam finishes on couture garments, the binding is applied to seam allowances which are themselves variable; estimate from the seam length, not perimeter. For bias-cut garments (the entire garment cut on the bias for drape and stretch), bias tape is rarely needed; use seam finishes appropriate to bias construction. And for ready-made packaged bias tape, just buy a package or two more than the calculation suggests — packaged bias tape is cheap, and running short mid-project is painful.