What Is Bias Tape? Uses in Sewing and Garment Finishing

Bias tape is created by cutting strips of fabric at a forty-five-degree angle to the selvage, which positions the fabric's greatest stretch along the length of the strip. This stretch is what distinguishes bias tape from straight-grain tape and is the reason bias tape can navigate curves without distortion. After cutting, the raw edges of the strip are pressed toward the center to form the fold. Single-fold bias tape has both edges folded to the center, creating a strip with a visible center line. Double-fold bias tape adds an additional fold down the center, encasing the raw edges entirely and producing a strip that wraps around a fabric edge like a sandwich.

Commercially produced bias tape is available in standard widths, typically one-half inch and one inch when folded, and in a range of solid colors and prints. Custom bias tape is made in the designer's chosen fabric, which is particularly valuable when the binding needs to match or coordinate with the garment. Making custom bias tape requires a continuous bias strip, which can be cut individually and joined with diagonal seams or produced using the continuous bias method where a tube of fabric is cut along a marked spiral line.

Single-fold bias tape is used primarily for enclosing seam allowances and finishing raw edges inside the garment. It is opened flat, stitched to the raw edge with one fold, then wrapped over and stitched again to enclose the edge. This produces a bound seam that resists fraying and adds a professional interior finish. It is common in unlined jackets, where the inside seam finishing is visible when the garment is worn open.

Double-fold bias tape wraps around the fabric edge and is stitched through all layers in one pass. This technique is used for neckline and armhole binding on garments like tank tops, baby clothes, and casual knit tops. It is faster to apply than single-fold because it requires only one line of stitching. The finished result shows a narrow band of binding on both the right and wrong sides of the garment.

Accurate cutting is essential for clean bias tape. The strips should be cut at a precise forty-five-degree angle using a rotary cutter and quilting ruler on a self-healing mat. The width of the cut strip depends on the desired finished width and the number of folds. A general formula is to cut the strip four times the desired finished binding width. For example, a finished binding of one-half inch requires a two-inch-wide strip.

When multiple strips are needed, they are joined with diagonal seams that distribute bulk evenly. To join two strips, they are placed right sides together at a ninety-degree angle and stitched diagonally from corner to corner. The excess is trimmed and the seam is pressed open. This method creates a smooth, nearly invisible join that lies flat when the tape is applied. Bias tape makers, which are small metal or plastic tools, fold the raw edges as the strip is pulled through, making it easy to press consistent folds along the entire length.

In production, bias binding is typically applied using a specialized binding attachment on the sewing machine. This folder feeds the bias strip and the garment edge simultaneously, wrapping the tape around the edge and positioning it for a single pass of stitching. Binding folders come in different sizes to accommodate various tape widths and are calibrated to produce consistent results at high speed. Operators trained on binding attachments can finish dozens of garments per hour with uniform results.

For curved edges, slight easing of the bias tape is required on the outer curve and gentle stretching on the inner curve. This is where the bias grain becomes critical. Straight-grain tape would pucker on curves, but bias-cut tape naturally accommodates the shape change. When specifying bias binding in a tech pack, include the finished binding width, the fabric source, the color, and the attachment method, noting whether the binding is applied with a folder or by hand.

Beyond its functional role, bias tape is a powerful design tool. Contrasting bias binding can define the silhouette of a garment, drawing attention to necklines, hems, and edges. Designers use printed, striped, or textured bias tape to add a layer of detail that is subtle but distinctive. In children's wear and activewear, brightly colored bias binding serves as both a finish and a visual accent.

Liberty-print cotton bias, silk charmeuse bias, and grosgrain-backed bias are all used in different market segments to achieve specific aesthetics. Designers working with digital tools like Skema3D can preview bias tape finishes on 3D garment models, testing color combinations and placement before committing to physical samples.

Quality issues with bias tape include inconsistent width, puckering on curves, and binding that does not enclose the raw edge completely. In production, binding width should be measured at regular intervals, and the garment should be inspected from both sides to ensure the tape catches on the underside. Shrinkage testing is also important. If the bias tape fabric shrinks differently from the garment fabric, the binding will pucker after the first wash. Pre-shrinking the bias tape fabric before cutting is a standard prevention step.

Colorfastness testing is essential when a contrasting bias tape is used, especially on light-colored garments. Dye migration from the binding to the base fabric during laundering or pressing can ruin the garment. Testing the bias tape and garment fabric together through the intended care process catches this issue before production.