How to Sew Mitered Corners: A Clean Finish for Hems and Bindings

A mitered corner is the small clean diagonal fold you see at the corner of a quality napkin, tablecloth, blanket, or scarf. Instead of the lumpy fold-over-fold you get from a basic double hem, a miter produces a 45-degree seam at each corner — flat on both sides, with no bulk, no fraying tail of folded fabric.

It’s not a difficult technique. It’s a precise one. Once you’ve done two or three, mitered corners take maybe 30 seconds longer per corner than a basic hem and look dramatically more polished.

When to miter

Use mitered corners on rectangular projects where:

• The hem is wider than 1 cm (very narrow hems can fold neatly without mitering).
• The corner will be visible (napkins, runners, table linens, blankets, scarves).
• You want a flat, professional-looking finish.

Skip mitering when:

• The hem is very narrow (5 mm or less — too small for a miter to register).
• The fabric is bulky (thick wool, towel terry — mitering creates an uneven thick wedge).
• The corner is hidden inside a lined piece (no one will see it).

The geometry behind it

A square corner has a 90° angle. To fold both perpendicular edges over by the same amount and have them meet flat at the corner, you need to remove the corner overlap with a 45° diagonal cut or fold. That’s the miter.

There are two methods:

• Folded miter (no cutting): you fold the corner down, then fold the two edges over the diagonal fold. Faster but slightly bulkier.
• Cut miter (with diagonal seam): you cut away the corner triangle, then sew a diagonal seam where the two folds meet. Cleaner but takes more time.

For most home sewing projects, the cut miter is worth the extra step — the result is genuinely flat.

What you need

• The project piece, hemmed-but-not-yet-finished (we’ll explain the order below).
• An iron and ironing board.
• A pencil or fabric marker.
• A clear ruler.
• Sharp shears.
• A sewing machine.

Method 1: The cut miter (recommended)

This is the standard technique for napkins, table runners, and similar pieces.

We’ll use a 2 cm hem for the example. Adjust the numbers proportionally for other widths.

Step 1: Mark the hem fold lines

On the wrong side of your fabric, draw two parallel fold lines along each edge:

• The first line at 1 cm from the raw edge.
• The second line at 2 cm from the raw edge.

This creates a double fold of 1 cm + 1 cm = 2 cm finished hem width. Mark both lines clearly.

Step 2: Identify the miter corner

At each corner, the two adjacent edges’ fold lines cross. Mark the point where the outer fold lines (the 2 cm lines) intersect — that’s the corner of the finished hem. Call this point A.

Now mark the points where the outer fold line of one edge meets the raw edge of the other (point B), and where the outer fold line of the second edge meets the raw edge of the first (point C). Points B and C should be 2 cm from the corner of the fabric, along each adjacent edge.

Step 3: Draw the miter cutting line

Draw a straight line from B to C. This line passes through point A — it’s the diagonal cutting line.

Step 4: Cut the corner

Cut along the BC line, removing the small corner triangle. You’re left with a flat diagonal edge across the corner.

Step 5: Press the diagonal fold

Fold the diagonal cut edge inward along an imaginary line that runs perpendicular to the hem corner. Press flat. The diagonal edge now runs at 45° from the hem corner.

Step 6: Press the two hem folds

Fold each adjacent edge in along the first fold line (1 cm from the original raw edge), then fold again along the second fold line (the 2 cm line). The two folds meet at the corner with a clean 45° join.

Step 7: Stitch

Sew along the inner edge of the hem (about 5 mm from the inner fold line) to secure the hem. The miter sits cleanly at the corner; the diagonal fold is enclosed inside.

For an even cleaner finish, you can hand-stitch the diagonal fold itself with a few invisible slip stitches (covered in our 10 essential hand stitches guide) to keep it from opening.

Method 2: The folded miter (no cutting)

Faster, slightly bulkier, used when fabric thickness is moderate and you don’t want to commit to a cut.

Step 1: Press the double-fold hem on each edge

Fold each edge over twice — first by 1 cm, then again by 1 cm — and press flat.

Step 2: Open out the second fold at one corner

Unfold the second fold (the 1 cm fold-over) along the two edges that meet at one corner. The first fold (the 1 cm raw-edge-tucked-in) stays in place.

Step 3: Fold the corner diagonally

At the corner where you’ve opened out the folds, fold the corner of the fabric inward at a 45° angle so that the diagonal fold passes through the corner of the inner fold lines (the original first-fold line you kept folded).

Press the diagonal fold flat.

Step 4: Re-fold the second fold

Now fold the second 1 cm hem fold back into place along both edges. The two re-folds should meet at the diagonal you just made — forming the miter.

Step 5: Stitch

Sew along the inner edge of the hem as in Method 1.

The folded miter has a small extra layer of fabric inside the corner. On lightweight fabric this is invisible. On heavy fabric it can be slightly bulky.

Common mitering mistakes

The corner doesn’t lie flat

Most often: the inner folds aren’t at exactly the same width on both edges. If one edge is hemmed at 18 mm and the other at 20 mm, the corner pulls. Press carefully and measure both sides identically.

The diagonal seam is visible from the right side

A folded miter sometimes shows a small fold line through lightweight fabric. Switch to a cut miter (Method 1) — the diagonal seam is on the wrong side only.

The miter “sticks out” past the corner

You cut the diagonal too close to the corner. The fabric isn’t fully tucked under. Recut wider next time.

The miter “leaves a gap”

You cut the diagonal too far from the corner. There’s not enough fabric to close the join. The corner shows the wrong side. Practise on scrap to dial in your measurement.

Practising on scrap

Cut a 25 × 25 cm square of scrap cotton. Mark the hem fold lines as described above (try a 2 cm hem to start). Miter all four corners, hem the edges, and inspect the result. Compare it to a non-mitered version (just fold-over-fold) on a second scrap.

The difference is striking. Once you’ve mitered a complete piece end-to-end, you’ll see exactly where the technique improves the finished look.

Mitered corners on bias binding

A close cousin: mitering applied bias binding around an outside corner.

When you wrap bias tape around the outside corner of a quilt or apron, you need to fold a tiny pleat at the corner so the binding lies flat on both sides. This is a 45° fold tucked behind the corner, usually pinned and then stitched as the binding continues.

The principle is the same as a hem miter: removing or folding the corner overlap so two perpendicular paths can meet at 90° without bunching.

When the corner isn’t 90°

Hexagonal placemats, octagonal table runners, irregular shapes — same principle, different fold angle. If the corner is 120° (hexagon), the diagonal fold is at 60°. The math: the diagonal angle equals (180° − corner angle) ÷ 2.

For odd-shaped projects, work out the geometry once on scrap fabric before committing to the real piece.

Closing thought

Mitered corners are one of those small technique upgrades that lift a project from “homemade” to “intentional.” Napkins, table runners, blankets, and scarves all benefit. The technique transfers — once you can miter a 90° hem corner, the same logic handles any rectangular hem you encounter.

For other small upgrades to beginner finishing, our 10 essential hand stitches guide covers the slip stitch and other invisible-from-outside techniques that pair well with mitered corners. The combination — mitered corner secured with hand-finished slip stitches — is the standard for higher-end home textiles.