The core method: pin, stitch, and ease as you go
Sewing bias tape around a curve works because bias tape is cut on the diagonal grain of fabric, which gives it natural stretch. The tape bends without creasing if you ease it gently into the curve as you stitch. The key is pinning the tape to follow the curve before you sew, then stitching slowly enough to feel when the tape wants to bunch, and stopping to re-pin if it does.
Start by pinning the bias tape to the wrong side of your fabric along the curve, placing pins every inch or so. Pin perpendicular to the edge — not parallel — so the pins hold the tape in place without distorting it. As you pin, gently stretch the tape just enough that it lies flat against the curve without wrinkles. You are not pulling hard; you are coaxing it to follow the line.
Stitch with a standard presser foot and a stitch length of 2.0 to 2.5 mm. Sew slowly, watching the tape ahead of the needle. If you see it starting to bunch or pucker, stop with the needle down, lift the presser foot, re-pin that section, and continue. This stop-and-adjust method takes longer than a straight seam but prevents the tape from twisting as you sew.
Key Takeaways
- Pin bias tape perpendicular to the edge every inch, stretching it gently so it follows the curve without wrinkles.
- Stitch at 2.0 to 2.5 mm length and watch ahead of the needle for bunching; stop and re-pin if the tape starts to twist.
- Fold the tape to the back of the fabric after the first seam, then stitch it down by hand or machine using a ladder stitch or edge stitch for an invisible finish.
- Concave curves (inward curves) need less stretch than convex curves (outward curves), so adjust your pin tension accordingly.
- Test your curve on scrap fabric first, especially on tight curves like armholes or necklines, to find the right pin spacing and stretch for your fabric weight.
Pinning strategy for different curve shapes
A convex curve — one that bulges outward, like the hem of a circle skirt — needs the tape stretched slightly as you pin. The outer edge of the tape is longer than the inner edge, so gentle tension helps the tape lie flat. Pin every three-quarters of an inch on a gradual curve, or every half inch on a tight curve like an armhole.
A concave curve — one that curves inward, like a neckline — needs almost no stretch. The inner edge of the tape is longer, so the tape naturally wants to bunch on the inside. Pin the same way, but do not pull; let the tape ease into the curve on its own. If you see wrinkles on the inside of the curve, you have pinned too tightly.
On very tight curves — a small armhole or a deep V-neck — place pins closer together and consider making small clips into the seam allowance of your fabric (not the tape) to help it bend. Clips should be perpendicular to the edge and stop just short of your stitch line.
Stitching the first seam without puckering
Use a standard presser foot and thread that matches the tape or the fabric, depending on which side will show. Stitch along the inner fold of the bias tape — the line where the tape was originally folded when it was made. This line is your guide and keeps your stitch distance consistent.
Sew at a steady, moderate speed. Fast stitching on a curve often causes the tape to shift under the presser foot, creating puckers. Slow stitching gives you time to feel the tape and adjust if it starts to twist. Every few inches, stop with the needle down, lift the presser foot, and check that the tape still lies flat ahead of the needle. If it has bunched, remove the pins in that section, smooth the tape, and re-pin before continuing.
If puckering appears after you have finished the seam, you can sometimes fix it by gently pulling the tape away from the fabric while pressing with steam. If the pucker is severe, unpick that section and re-stitch it, re-pinning more closely.
Finishing the tape on the back side
After the first seam is complete, fold the tape to the back of the fabric and find it. On a curve, the back side of the tape will be slightly fuller than the front because the tape has been eased into the shape. This fullness is normal and should be distributed evenly across the curve.
For an invisible finish, use a ladder stitch (also called a slip stitch). Thread a needle with thread that matches the tape, knot the end, and bring the needle up through the fold of the tape from inside. Slide the needle through the fold for a quarter inch, then bring it out and cross over to the fabric. Go into the fabric directly across from where you came out, slide the needle through the fabric for a quarter inch, and come back out. Cross back over to the tape fold and repeat. The stitches will be nearly invisible when pulled snug.
Alternatively, stitch the tape down by machine using a narrow zigzag or a straight stitch very close to the inner fold of the tape. This method is faster and holds well on curves because the zigzag gives slightly as the fabric moves.
Handling tight curves like armholes and necklines
Armholes and necklines curve sharply and often in both directions — convex at the shoulder and concave at the neck. Break the curve into sections. Pin and stitch the convex part first, easing the tape gently. Then move to the concave section and let the tape ease without tension. At the transition point, you may need to stop, unpin, smooth everything, and re-pin to avoid a sudden pucker.
On a very tight curve, consider using single-fold bias tape instead of double-fold. Single-fold tape is thinner and bends more easily. You will need to fold the raw edges under as you stitch, but the result is less bulk and fewer puckers on sharp curves.
Test your approach on a scrap of the same fabric before committing to your garment. Sew a practice curve, finish it, and see how it looks. Tight curves often need pins every half inch and very slow stitching to come out smooth.
Pressing and setting the seam
After stitching the first seam, press the tape flat against the fabric using a pressing ham or a rolled towel under the curve. A ham supports the curve and prevents you from flattening it. Use steam and medium heat, pressing from the fabric side first, then from the tape side. Let the fabric cool before moving it.
Press again after you have finished the back side. This sets the stitches and helps any remaining small puckers relax into the fabric. On a curve, pressing is as important as stitching because it helps the tape and fabric bond and settle into their final shape.
Common mistakes and how to avoid them
Pinning the tape parallel to the edge instead of perpendicular is the most common error. Parallel pins do not hold the tape in place; they let it shift as you sew. Always pin perpendicular — straight into the fabric, at right angles to the edge.
Stretching the tape too much on a concave curve causes bunching on the inside. Remember: concave curves need little to no stretch. Let the tape ease naturally and trust the bias grain to do the work.
Stitching too fast on a curve often causes the presser foot to push the tape out of alignment. Slow down, watch ahead of the needle, and stop to re-pin if you see the tape starting to twist. A few extra minutes of careful stitching saves the time you would spend unpicking and re-doing.
Skipping the press step leaves puckers that could have been relaxed away. Always press after the first seam and again after finishing the back. Steam and time do much of the work that careful stitching alone cannot.
Frequently Asked Questions
Why does my bias tape pucker even though I pinned it carefully?
Puckering usually means the tape was stretched too much or the stitching was too fast for the curve to settle. Try re-stitching that section with the tape pinned more loosely and your machine set to a slower speed. Pressing with steam afterward often relaxes small puckers that stitching alone cannot fix.
Can I use regular tape instead of bias tape on a curve?
No. Regular tape is cut on the straight grain and does not stretch. It will wrinkle and bunch on any curve. Bias tape is cut diagonally, which gives it the stretch needed to bend smoothly. If you do not have bias tape, you can make your own by cutting strips on the diagonal and joining them end to end.
How close should my pins be on a very tight curve?
On a tight curve like an armhole, place pins every half inch. On a gradual curve, every three-quarters to one inch is usually enough. The tighter the curve, the closer the pins. If you see bunching between pins as you stitch, move them closer together next time.
Should I clip the seam allowance before explore bias tape?
On a concave curve (inward curve), small clips perpendicular to the edge help the fabric bend without bunching. Clips should stop just short of your stitch line. On a convex curve (outward curve), clips are usually not needed because the tape stretches to accommodate the shape.
What is the difference between ladder stitch and edge stitch for finishing the back?
Ladder stitch is nearly invisible because the thread runs inside the fold of the tape. Edge stitch is a straight line of stitching close to the fold and is visible from the back. Ladder stitch takes longer but looks more polished. Edge stitch is faster and holds just as well, especially on curves where the tape is eased.