Bias Binding Planner
Plan bias tape or quilt binding: strips, joins and fabric from yardage or from one square, with a to-scale cutting diagram. Everything runs in your browser; nothing is uploaded.
Method 1: strips cut on the bias from yardage
Method 2: one continuous strip from a square
Fabric lengths and strip totals are rounded up to the next 1/8 in or 0.5 cm, and lengths you will get from a given fabric are rounded down, so no figure is shown more precisely than you can cut it.
How it is calculated
Every number below comes from the formulas here; none is looked up from a chart. Lengths are in one unit, and the inch and centimeter views use the exact factor 2.54 cm per inch.
Cut width and length needed
- Cut width = finished width × multiplier + extra width. The multiplier defaults to 4. For quilt binding you enter the cut width itself.
- Length needed L = sum of edges × 1.05 (if waste is on) + extra length.
- Joins. Each diagonal join uses up some strip length. If each strip is sewn a distance a in from its 45° cut end, the loss along the strip is 2 × a × √2, which is 0.71 in for a ¼ in seam. The default of 0.5 in (1 cm) is a round figure; change it to match your seam.
Method 1: strips from yardage
Set the fabric with x across the width Wu (usable width, after the selvedge allowance) and y down its length. A 45° strip of width w covers the band between two lines y − x = t; its vertical thickness is h = w√2. A pass that runs from one selvedge to the other is a parallelogram whose ends already lie at 45° to the strip, so they are ready to join.
- Length of one full pass: s = Wu × √2. At Wu = 44 in, s = 62.23 in.
- Strips: the smallest N with N × s − (N − 1) × j ≥ L, so N = ⌈(L − j) ÷ (s − j)⌉ and joins = N − 1.
- Fabric length: Y = Wu + N × w × √2, then rounded up. The two triangles at the ends, Wu² of cloth in all, are unused in this layout.
- Worked example: Wu = 44 in, w = 2 in, L = 300 in, j = ½ in. N = ⌈299.5 ÷ 61.73⌉ = ⌈4.85⌉ = 5 strips, 4 joins, Y = 44 + 5 × 2.83 = 58.14 in, so 58¼ in.
- Corner offcuts. The optional layout also cuts the shorter bands that fit in the two end triangles. Each band is a strip whose ends are cut by the selvedge or by the fabric end; its centerline is √2 × (x range). Bands that cross a fabric corner and pieces shorter than half a full pass are not used, because every extra piece is another join. It never needs more fabric than the full-pass layout, and often needs less when the job is small, at the cost of more joins.
Method 2: continuous bias from a square
A square of side S has area S². A strip of width w and length ℓ has area ℓ × w, so ℓ ≈ S² ÷ w before seam losses, and S = √(L × w) for the length you need. A 36 in square cut into 2 in strips gives 36² ÷ 2 = 648 in. Published guides round the side up and add about 2–3 in for the tube seam and the short end pieces, so the planner adds an allowance (default 2 in, 5 cm) and reports the length that square will actually give, (S − allowance)² ÷ w. Set the allowance to 0 to see the ideal figure.
Limitations
- Fabric stretches on the bias. Strips lengthen as you press, pull and sew them, so the real binding can end up longer than planned. Do not stretch it, and test a scrap.
- Directional prints, stripes and plaids change which layout looks right; the planner treats the cloth as plain. Pattern matching at joins needs extra length.
- Bias binding is used on curves because it stretches to follow them. We could not find a source that gives a length factor for curves, so the planner does not guess one. Measure the curve with a flexible tape and enter that as an edge.
- Corners, mitered corners, and the overlap where the ends meet need extra length; sources quoted below add 10 to 20 in for a quilt. Use the extra-length field.
- The cutting diagram is a layout aid, not a pattern: it assumes you can cut straight 45° lines, and it does not shrink the cloth for pre-washing.
- Conventions for cut width differ between sources (single-fold versus double-fold, seam allowances, batting thickness). The multiplier and extra width are editable for that reason.
Sources
- Bias Binding – The Basics + Beyond, Sew4Home. Square-root method (156 in × 2 in, √312 = 17.66, rounded up and plus 2–3 in for seaming); cut width four times the finished width, with a double-fold variant that adds twice the seam allowance; ¼ in seam to join strips.
- How to Make Continuous Bias Binding, Sew4Home. Worked example of a 21 in square cut into 2 in strips with ¼ in seams; remove the selvedges before measuring the square; add ¼ in to the cut width for batting.
- 9 Steps to Making Continuous Bias Binding, Quilt Social. Length × strip width = area; square root, rounded up. Example: 274 in × 2.5 in = 685, √685 = 26.17, so a 27 in square. States that cutting separate bias strips takes more fabric than the square.
- Make Double-Fold Binding for Your Quilt, Dummies. Cut strips four times the finished binding width (½ in finished, 2 in strips).
- Bias tape, Wikipedia (used to locate references and definitions). Single-fold and double-fold definitions; widths are quoted flat; folded tape is about a quarter of the strip width.
- Binding a Quilt, Utah State University Extension. Quilt binding strips cut 2¼ in (2½ in for thick quilts); ends cut at 45° and joined with a ¼ in seam; perimeter plus 10 in for seams and corners.
- How Wide to Cut Quilt Binding, Sew Nikki. Most binding is cut 2–2.5 in wide; ¼ in joining seams; 15–20 in of extra length.
Opened and read 16 October 2026. The geometry (bias strip layout, join loss, corner pieces) is derived on this page and checked by unit tests, not taken from these sources.
Bias binding is a strip of woven cloth cut at 45 degrees to the weave, which gives it enough stretch to wrap a curved edge flat. The planner on this page tells you how many strips, how many joins and how much fabric you need, by two methods, with a to-scale cutting diagram.
What is bias binding?
Bias binding, also sold as bias tape, is a narrow strip of fabric used to finish a raw edge. It is folded over the edge and stitched, and it turns up on quilts, placemats, bibs, armholes and necklines. Tape that is not pressed in half lengthwise is called single-fold; tape that is pressed in half is double-fold. Folded tape ends up about one quarter of the width of the strip it was made from.
Why cut it on the diagonal?
A woven cloth hardly stretches along its grain, but across the diagonal it gives. That diagonal is the bias, and a strip cut there follows a curve instead of puckering. The same give is why a bias cut garment drapes over the body. Quilters often skip it: one university extension guide teaches straight-grain binding and says bias is not needed unless the edge is curved, while another quilting tutorial says a curved edge must have it.
How wide should the strip be?
Sources disagree, which is why the planner lets you change the number. The common rule is four times the finished width, so a half-inch binding is cut 2 inches wide. One source adds twice the seam allowance for double-fold, giving 3 inches for a half-inch finished width with a half-inch seam. Quilt binding is usually quoted as a cut width instead.
| Convention | Rule | Example |
|---|---|---|
| Four times finished | finished × 4 | ½ in finished, 2 in strip |
| Double-fold with seams | 2 × seam + 4 × finished | ½ in seam, ½ in finished, 3 in strip |
| Quilt binding | cut width stated directly | 2 to 2½ in, often 2¼ in |
How does the planner work out the fabric?
Method 1 cuts separate 45° strips from yardage. A strip that runs from selvage to selvage across cloth of usable width W is √2 × W long, so 44 inches of cloth gives strips of about 62¼ inches. Each diagonal join uses up a little of that length. The planner finds the smallest number of strips that still reaches your length after the joins, then adds the length of cloth they occupy: W plus the number of strips times the cut width times √2. The two triangles at the ends are treated as waste unless you switch on the corner-offcuts layout. For 300 inches of 2 inch strips on 44 inch cloth that gives 5 strips, 4 joins and 58¼ inches of fabric.
Method 2 spirals one square into a single strip. A strip of width w and length ℓ covers an area of ℓ × w, so a square of side S yields about S² ÷ w before losses. A 36 inch square cut at 2 inches gives about 648 inches. Run backwards, the square you need is √(length × width). Published guides round up and add a few inches for the seam and the short ends, so the planner adds an allowance you can change.
Which method should I use?
A quilting tutorial notes that cutting separate bias strips takes more fabric than using a square. At the defaults, 300 inches of 2 inch binding needs 26½ inches of cloth as a square against 58¼ inches as full-width strips, or 26¼ inches if you also use the corner offcuts. The square has no joins to sew and suits a long continuous binding. Separate strips suit a short binding, narrow fabric, or a square that would be wider than the cloth.
What does it not know?
Bias stretches as you handle it, so test a scrap and do not pull. Directional prints and plaids need extra for matching. The planner has no factor for curves, because we did not find a source for one; measure the curve and enter it as an edge. Corners and the overlap where the ends meet need extra length, and the extra-length field is there for that. Every figure is rounded up to the next ⅛ inch or half centimeter, and the geometry is checked by unit tests against hand-worked examples.