Definition
Bias binding is a narrow strip of fabric cut on the bias, usually with folded edges, used to enclose raw edges and finish curves such as necklines and armholes.
Cut at 45 degrees to the grain, a strip of woven fabric stretches and bends smoothly around curves without rippling. That is why binding for necklines, armholes, curved hems and quilt edges is cut on the bias.
Two kinds, by how they are folded:
- Single-fold: both long edges folded to the center. Used as a bias facing, turned fully to the inside so it does not show.
- Double-fold: single-fold binding folded again in half. Used as a binding that wraps the edge and shows on both sides.
To make your own, cut strips four times the finished width: a 4 cm (1 1/2 in) strip gives a 1 cm (3/8 in) double-fold binding. Join strips with diagonal seams to avoid bulk, and press the folds with a bias tape maker. Binding made from the garment fabric or a contrast cotton usually looks better than ready-made tape.
Apply it slightly stretched on inward curves such as a neckline, so it pulls the edge in and lies flat, and without stretching on outward curves. On knits, use a strip of the knit cut across the grain instead.
To work out how many strips and how much fabric you need, use the bias binding calculator. Step by step: finishing necklines and armholes with bias binding.