Bias binding calculator
Add up the edges to bind, choose the finished width and the type of binding: you get the binding length, the width to cut the strips and the size of fabric square that makes it as continuous bias.
The width you see on the right side.
Side of the square you will cut the bias from.
Your binding
Strips are cut at 45° to the selvedge (true bias). Add 2 to 3 mm (1/8 in) to the strip width on thick fabric.
Measure every edge you want to bind and add about 5 cm (2 in) per edge for joining the ends. Cut strips 6 times the finished width for double-fold (French) binding, or 4 times for single-fold. A square of fabric gives about side × side ÷ strip width of continuous bias, less around 10 % for the seams and the ends.
How much bias binding do I need?
Measure each edge along the stitching line with the tape on its side, following the curve: the neckline, each armhole, the hem. Add the extra for the joins. For a sleeveless top with a 60 cm neckline and two 45 cm armholes: 60 + 5 + 2 × (45 + 5) = 165 cm (65 in) of binding. In inches, a 24 in neckline and two 18 in armholes with 2 in per edge come to 66 in.
Bias binding is cut on the bias, at 45° to the selvedge, because only bias strips stretch enough to lie flat around a curve. Staystitch curved edges before binding them so they keep their shape.
How wide should I cut bias strips?
| Binding | Strip width | 6 mm (1/4 in) finished | 1 cm (3/8 in) finished | 1.2 cm (1/2 in) finished |
|---|---|---|---|---|
| Double-fold (French) | 6 × finished width | 3.6 cm (1 1/2 in) | 6 cm (2 1/4 in) | 7.2 cm (3 in) |
| Single-fold | 4 × finished width | 2.4 cm (1 in) | 4 cm (1 1/2 in) | 4.8 cm (2 in) |
Double-fold binding is pressed in half lengthwise before you sew it, so it has two layers: it is sturdier, easier to sew neatly, and the usual choice for necklines and armholes. Single-fold binding is one layer with its edges pressed in, flatter on thick fabric. On thick fabric, add 2 to 3 mm (1/8 in) to the strip width so the binding still wraps the edge.
How much binding does a square of fabric make?
For continuous bias, cut the square in half along the diagonal, sew the two triangles into a parallelogram, mark lines one strip width apart, sew it into a tube with the lines offset by one strip, and cut along the spiral. The length is about the square's area divided by the strip width.
- Metric: a 50 cm square cut into 6 cm strips gives 2,500 ÷ 6 ≈ 417 cm, about 3.75 m after the seams.
- Imperial: a 20 in square cut into 2 1/4 in strips gives 400 ÷ 2.25 ≈ 178 in, about 160 in (4 1/2 yd) after the seams.
To find the square you need, work backwards: side = √(length × strip width ÷ 0.9). The 165 cm top above with 6 cm strips needs √(165 × 6 ÷ 0.9) ≈ 34 cm, a 34 cm (13 3/8 in) square.
For a short length, separate strips are simpler: the calculator shows how many strips the square gives across its diagonal. Join them with diagonal seams so the joins spread out and do not make a lump.
Finishing necklines and armholes with bias binding shows how to sew it on, from the first pass to the final edgestitch.
Frequently asked questions
How wide do I cut bias strips for 1 cm (3/8 in) binding?
6 cm (2 1/4 in) for double-fold binding and 4 cm (1 1/2 in) for single-fold. On thick fabric add 2 to 3 mm (1/8 in) so the binding still wraps around the edge.
How much bias binding do I need for a neckline and armholes?
Measure the neckline and each armhole on the stitching line and add about 5 cm (2 in) per edge for the joins. A sleeveless top typically needs 1.5 to 2 m (1 3/4 to 2 1/4 yd).
Do I have to cut binding on the bias?
For curves, yes: only bias strips stretch enough to lie flat around a neckline or armhole. Straight edges, such as the top of a tote bag, can use strips cut on the straight grain, which use less fabric.
Can I buy bias binding instead of making it?
Yes. Ready-made bias tape is sold by its folded width, in single-fold and double-fold. Making your own lets you match the fabric of the garment and choose a lighter, softer binding.