Sew strips end-to-end at a 45-degree angle for a clean, continuous binding

The standard method is the diagonal seam, which joins two strips so the seam runs corner-to-corner rather than straight across. This angle lets you press the seam open flat, and when you fold the binding in half lengthwise, the seam disappears into the fold. The result is a binding with no visible joins on either side of the quilt.

You will need two strips cut to your binding width (usually 2.5 inches for quilting), placed right sides together at a 90-degree angle to each other, forming an L shape. Mark a diagonal line from the inside corner to the outside corner, sew along that line, trim the excess, and press. Chain several strips this way and you have one long piece ready to attach to your quilt.

Key Takeaways

  • The diagonal seam method joins strips at 45 degrees so the seam sits hidden inside the binding fold.
  • Place strips right sides together in an L shape, mark the diagonal from inside corner to outside corner, and sew along that line.
  • Trim the excess fabric to a quarter inch from the seam, then press the seam open to keep bulk out of the binding.
  • Chain multiple strips together before cutting them apart to save time and thread.

Setting up the strips in an L shape

Lay your first strip flat on the cutting mat with the right side up. Take your second strip and place it right side down on top of the first, but rotated 90 degrees so the two strips form an L. The corner of the top strip should meet the corner of the bottom strip at the inside angle of the L. The excess fabric will stick out on two sides.

This positioning is the key to the whole method. If the strips are parallel or only slightly angled, the seam will be too shallow and the binding will bunch. If they are at a true right angle, the diagonal seam will run at exactly 45 degrees, which is what you want.

Marking and sewing the diagonal line

Use a pencil or fabric pen to draw a line from the inside corner (where the two strips meet) to the outside corner (the farthest point from that meeting). This line should run diagonally across the overlapped fabric. A quilter's ruler with a 45-degree angle marked on it makes this faster, but a regular ruler and a pencil work just as well.

Sew directly on the line you marked. Use a regular stitch length (around 2.5 on most machines) and backstitch at both ends. The seam does not need to be perfect — it just needs to be on the line. After sewing, check that both strips lie flat and the seam is find before you trim.

Trimming and pressing the seam

Once the seam is sewn, you will have two triangular flaps of excess fabric sticking out from the corners. Trim these flaps to a quarter inch from the seam line. Use a rotary cutter and ruler for a clean edge, or scissors if you prefer. This quarter-inch allowance prevents fraying and gives you a small margin if the seam shifts slightly when you press.

Press the seam open with an iron set to medium heat. Do not press it to one side — opening it flat keeps the binding from becoming too thick at the seam. Once pressed, the joined strips should lie flat and the seam should be invisible when you fold the binding in half.

Chaining strips to save time

If you are joining many strips, arrange them all in L shapes before you start sewing. Mark the diagonal line on each pair. Then sew them one after another without cutting the thread between seams — this is called chain piecing. The thread chain connecting them uses almost no fabric and costs nothing to cut away later.

After all the seams are sewn, trim the thread chain and cut apart the individual joined pairs. Trim the excess corners and press all the seams open. Then join the pairs into longer segments, and keep going until you have one continuous strip long enough for your binding.

Joining multiple segments into one long strip

Once you have several two-strip segments, join them the same way: lay them in an L, mark the diagonal, sew, trim, and press. You can chain these together too. Keep joining segments until the strip is long enough to go around your quilt plus 10 to 12 inches for overlap and seaming the ends together.

Measure your quilt perimeter before you start joining, so you know when to stop. A typical lap quilt needs 280 to 320 inches of binding; a bed quilt needs 400 to 500 inches. It is better to have a few extra inches than to run short and have to join one more segment at the last minute.

Pressing and storing the finished binding strip

Once all the seams are joined and pressed, fold the entire strip in half lengthwise with wrong sides together and press the fold. This is the binding in its finished form — ready to attach to your quilt. The diagonal seams will now be hidden inside the fold, and the binding will look like one continuous piece on both sides of the quilt.

If you are not attaching the binding right away, roll it loosely and store it flat or in a bag. Do not fold it tightly or leave it creased, because the crease will be hard to press out later. A loose roll keeps the binding ready to use whenever you are ready to sew it to the quilt.

Frequently Asked Questions

Can I sew the strips straight across instead of diagonally?

You can, but the seam will create a thick ridge when you fold the binding in half. The diagonal seam distributes the fabric more evenly and presses flatter. Straight seams are faster but visible on the finished binding.

What if my diagonal seam is crooked?

A slightly crooked seam will still work. The important thing is that it holds the strips together securely. If the seam is very far off the line, you can cut it out and resew, but minor wobbles will not affect the binding's function or appearance.

How much fabric do I lose at each seam?

You lose roughly a quarter inch of length at each seam because of the trim. If you are joining 10 strips, plan for about 2.5 inches of total loss. This is why measuring your quilt perimeter and adding extra length before you start is important.

Do I have to press the seams open, or can I press them to one side?

Open seams are standard because they keep the binding thinner and flatter. Pressing to one side works but creates bulk at the seam, which can show as a ridge on the finished quilt. Open pressing takes a few extra seconds and gives a better result.

Can I use this method with strips of different widths?

Yes, but the seam will be less balanced. If you are mixing widths, mark the diagonal so it runs from the inside corner to the outside corner of the L shape, and the seam will still work. Most quilters cut all binding strips to the same width for consistency.