What a bias strip is and why you sew it

A bias strip is a long, narrow piece of fabric cut at a 45-degree angle to the grain of the cloth. When you sew it to an edge—a neckline, armhole, or the curved edge of a quilt—the diagonal cut lets the strip bend and curve without puckering or bunching. The strip itself becomes a finished edge that looks professional and wears well.

You cut bias strips from a larger piece of fabric, join them end-to-end into one long strip, press them in half lengthwise, and then sew them to your garment or project. The whole process takes about 30 to 45 minutes for a single garment neckline, depending on how much edge you are binding.

Key Takeaways

  • Bias strips are cut at a 45-degree angle to the fabric grain so they stretch and curve without puckering on necklines, armholes, and curved seams.
  • You cut parallel strips from your fabric, join them end-to-end with diagonal seams, and press the long strip in half lengthwise before sewing it on.
  • A rotary cutter and ruler make cutting faster and more accurate than scissors, but scissors work if you mark your lines carefully with a pencil.
  • Sew the bias strip to your garment with the raw edges aligned, then fold it to the back and hand-stitch or machine-stitch it down for a finished edge.
  • Common mistakes include cutting strips too narrow, not pressing the fold firmly, and sewing with uneven seam allowances.

Cutting bias strips from your fabric

Start with a square or rectangle of fabric larger than the total length of bias you need. For a child's shirt neckline, a 12-inch square is usually enough. For an adult garment or a quilt edge, you may need a piece 18 to 24 inches on each side.

Mark a line at a 45-degree angle across one corner of your fabric. If you have a rotary cutter and a 45-degree angle ruler, line up the ruler's diagonal edge with the fabric corner and cut along it. If you are using scissors, use a pencil to draw the line first, then cut slowly and straight. Discard the small triangle you cut off—this is just to establish the angle.

Now cut parallel strips across the fabric, all the same width. For most garment necklines, cut strips 2 to 2.5 inches wide. For quilts or thicker binding, cut 2.5 to 3 inches wide. Use your ruler to measure the distance between each line, or use a rotary cutter with a guide to keep the spacing even. You should end up with a stack of long diagonal strips.

Joining strips end-to-end

Lay two strips right sides together so they form an L shape, with the ends overlapping slightly. The short ends should meet at a 90-degree angle. Draw a diagonal line across the overlap from one corner to the opposite corner, or use a ruler to guide your eye. Sew along this diagonal line with a standard 1/4-inch seam allowance.

Trim the excess fabric at the corners to 1/4 inch from the seam, then press the seam open. Repeat this process until all your strips are joined into one long strip. Press the entire strip flat before moving to the next step. The seams should lie flat and not create thick bumps when you fold the strip in half.

Pressing the bias strip in half

Fold the long strip in half lengthwise with wrong sides together, so the two long edges line up. Press with a hot iron, using firm, steady strokes from one end to the other. The fold should be sharp and even. This creates the crease that will guide you when you sew the strip to your garment.

If your strip is very long, press it in sections rather than trying to handle the whole thing at once. A pressing ham or rolled towel under the fold helps the strip curve naturally without flattening. Let the strip cool before you move it—a warm crease can shift out of place.

Sewing the bias strip to your garment by machine

Pin the bias strip to the edge of your garment with raw edges aligned and the folded edge facing inward (toward the garment). Start at a seam or a point where the join will be hidden. Use a 1/4-inch seam allowance and sew slowly, especially around curves. The bias strip should bend smoothly without bunching.

When you reach the end, overlap the strips by about 1/2 inch and trim the excess. Fold the end of the starting strip back on itself and sew the overlap closed, then trim and press. Fold the bias strip to the back of the garment, covering the raw seam, and pin it in place. Sew it down by machine using a stitch close to the fold, or hand-stitch it with a ladder stitch for an invisible seam.

Hand-stitching the bias strip for a professional finish

After you sew the bias strip to the front of your garment, fold it to the back and pin it so the fold covers the raw seam line. Thread a needle with thread that matches your fabric and use a ladder stitch (also called an invisible stitch) to close it. Bring the needle out through the fold of the bias strip, then cross over to the garment and go in just below the seam line. Slide the needle inside the garment fabric for about 1/4 inch, then come back out and cross over to the bias strip fold again.

Work slowly and keep your stitches small—about 1/8 inch—so they do not show from the front. The thread should run inside the fold of the bias strip and inside the garment fabric, never on the surface. After every few stitches, gently pull the thread to close the gap, but do not pull so hard that you pucker the fabric.

Common mistakes and how to avoid them

Cutting strips too narrow is the most common error. Strips narrower than 2 inches are hard to handle and do not provide enough fabric to fold and sew securely. If your strips are too narrow, the bias binding will fray or come loose after washing.

Not pressing the fold firmly enough leaves the crease soft and unclear, making it hard to sew a straight line on the back. Press with a hot, dry iron and let the strip cool completely before you pick it up. Uneven seam allowances when you sew the strip to the garment create a wavy edge. Use a presser foot with a 1/4-inch guide, or mark your seam line with a pencil before you start.

Stretching the bias strip as you sew it on causes the edge to ripple and pucker. Let the strip feed naturally under the presser foot without pulling. If you are sewing around a tight curve, slow down and use shorter stitches (about 2 mm) so the fabric can turn smoothly.

Frequently Asked Questions

Can I use a bias tape maker tool to speed up the process?

Yes. A bias tape maker is a small metal tool that folds your strip in half as you feed it through. You pull the strip through slowly and press it as it comes out the other end. This cuts your pressing time in half, but you still have to cut and join the strips by hand first. The tool costs $8 to $15 and works well for long projects like quilts.

What if I do not have a rotary cutter?

You can cut bias strips with scissors and a pencil. Mark your 45-degree angle line with a ruler and pencil, then cut along the line slowly and carefully. It takes longer than a rotary cutter, but the result is the same. A long ruler and a sharp pencil help you keep the lines straight.

How much bias strip do I need for a neckline?

Measure the neckline opening with a soft measuring tape, then add 2 to 3 inches for overlap and seam allowances. For an adult shirt neckline, you usually need 24 to 30 inches of finished bias strip. For a child's garment, 18 to 22 inches is typical.

Can I sew bias strips on a curved edge like an armhole?

Yes, that is one of the main reasons to use bias strips. The 45-degree cut lets the strip stretch and bend around curves without puckering. Sew slowly around the curve and use a shorter stitch length (about 2 mm) so the fabric can turn smoothly. Do not pull the strip as you sew.

What thread should I use to sew the bias strip?

Use thread that matches your fabric color. For hand-stitching the back, use the same weight thread as your garment—usually all-purpose polyester or cotton. For machine-stitching, all-purpose thread works for most fabrics. If your fabric is very thick or stretchy, use thread designed for that fabric type.