The Basic Technique for a Squared Corner

A sewn corner on a blanket is made by folding the fabric at a 45-degree angle, then stitching along that fold so the two edges meet at a right angle when you flip it right-side out. The result is a corner with no bulk, no raw edges showing, and a crisp point—the same method used on pillowcases and quilt bindings.

The process takes about five minutes per corner once you understand the fold. You will need a needle (hand or machine), thread that matches your blanket, scissors, and a ruler or measuring tape. Most people find a sewing machine faster, but hand-sewing works just as well if you take small, even stitches.

Key Takeaways

  • Mark a diagonal line from the corner point at a 45-degree angle, then fold the fabric along that line so the two raw edges line up perfectly.
  • Stitch along the fold line, starting and stopping about one-quarter inch from the corner point to leave room for the seam allowance.
  • Trim the excess fabric at the corner to reduce bulk, then turn the corner right-side out and press it flat with an iron.
  • The seam allowance—the distance between your stitching and the raw edge—should be consistent (usually one-quarter to one-half inch) on both sides of the corner.

Marking and Folding the Corner

Lay your blanket flat on a table with the two edges you want to sew facing up. Place the corner point closest to you. Using a ruler and a pencil or fabric marker, draw a line from the corner point at a 45-degree angle—this line should run from the corner toward the inside of the blanket, roughly one-half inch from the point itself.

Fold the blanket so the two raw edges meet exactly on top of each other. The fold should follow the diagonal line you just drew. Press the fold with your fingers or a hot iron to crease it sharply. This crease is your stitching line. If the edges do not line up, unfold and adjust the fold until they do—misaligned edges will create a lopsided corner.

Stitching the Diagonal Seam

Thread your needle or prepare your sewing machine. If hand-sewing, use a backstitch, which creates a strong seam by pushing the needle backward through the previous stitch. If using a machine, set it to a standard straight stitch with a stitch length of 2 to 2.5 millimeters.

Start stitching along the crease about one-quarter inch away from the corner point. Stitch toward the outer edge of the blanket, keeping your line as close to the fold as possible. Stop stitching about one-quarter inch before you reach the outer edge. Backstitch a few stitches to lock the thread, then cut the thread and remove the blanket from the machine (or tie off by hand).

The reason you stop short of the corner point and the outer edge is to leave room for the seam allowance—the fabric between your stitching and the raw edge. If you stitch all the way to the point, the corner will be too thick to turn right-side out.

Trimming and Turning the Corner

Unfold the blanket and look at the corner from the wrong side (the side that will be hidden). You should see a diagonal seam with a triangular flap of fabric on each side. Using sharp scissors, trim these flaps down to about one-quarter inch from the seam. This removes bulk so the corner lies flat when turned.

Now fold the blanket right-side out along the two edges you originally wanted to sew. The diagonal seam you just stitched should be hidden inside the fold. Gently push the corner point outward with your finger or a blunt tool (a chopstick works well) until the corner is fully turned and squared off.

Pressing and Finishing

Lay the corner flat on an ironing board and press it with a hot iron set to the temperature appropriate for your blanket fabric. Press from both the right side and the wrong side to set the shape. A well-pressed corner will have a crisp, sharp point with no puckering.

Once all four corners are sewn and pressed, you can sew the two long edges of the blanket together if you have not already. If you are binding the edges (adding a strip of fabric around the perimeter), the corners will be easier to bind if they are already squared off.

Common Mistakes and How to Avoid Them

Misaligned edges: If the two raw edges do not line up when you fold, the corner will be crooked. Unfold and refold until the edges are perfectly flush. A light crease with an iron before stitching helps you see whether the fold is correct.

Stitching too close to the point: If you stitch right at the corner point, you will not have enough seam allowance, and the corner will be too bulky to turn. Always stop one-quarter inch short of the point. Similarly, do not stitch all the way to the outer edge—stop one-quarter inch before you reach it.

Not trimming the flaps: Leaving the full seam allowance on both sides of the diagonal seam creates a thick, lumpy corner. Trim the flaps to one-quarter inch or less so the corner lies flat.

Pressing too soon: If you press the corner before it is fully turned right-side out, you will set in creases that are hard to remove. Always turn the corner completely, square off the point, and then press.

Frequently Asked Questions

Can I sew a corner by hand instead of using a machine?

Yes. Use a backstitch, which is stronger than a running stitch and creates a seam that will not come apart with use. Make your stitches small and even—about one-eighth inch apart. Hand-sewing takes longer but gives you more control over the fold and the seam line.

What seam allowance should I use?

One-quarter to one-half inch is standard for blankets. The smaller the allowance, the sharper the corner point, but the less room you have for error. One-half inch is more forgiving if your fold is slightly off. Measure from the raw edge to your stitching line and keep it consistent on both sides of the corner.

What if my corner is still lumpy after I turn it?

You likely did not trim the flaps enough. Unfold the corner, trim the triangular flaps down to one-quarter inch or even one-eighth inch from the seam, then turn and press again. A very sharp corner may need the flaps trimmed even shorter.

Do I have to sew all four corners, or just the ones where two edges meet?

You only need to sew the corners where two raw edges meet. If one edge is already finished (bound or hemmed), that corner does not need the diagonal seam. Sew only the corners that have two raw edges facing outward.

Can I use this method on a blanket that is already sewn on three sides?

Yes, but you will need to work from the inside. Fold the blanket so the unsewn corner is accessible from the wrong side, mark and fold the diagonal, stitch, trim, and then turn the blanket right-side out through the opening. This is trickier than sewing all corners before assembly, so take your time with the fold.