A mitered corner joins two hems that meet at a corner along a 45° diagonal, so that the fabric inside the corner is folded away instead of stacked, and the corner lies flat with a crisp point. Press both hems, unfold them, fold the corner over on the diagonal through the point where the two crease lines cross, trim the corner to leave 1 cm (3/8 in), then refold the hems: the diagonal edges meet and are slipstitched or edgestitched. For a sewn miter, fold the corner right sides together on the diagonal and stitch across it from the hem crease to the turn-under crease before turning.
What do you need to miter a hem corner?
- A hem allowance that is the same on both edges, usually 2–5 cm (3/4–2 in) including a 1 cm turn-under for a double-fold hem. Equal widths give a true 45° miter; unequal widths can be mitered too, with a different angle, as explained below.
- An iron, a pressing surface and a clear ruler with a 45° line. A seam gauge helps keep the folds even.
- A fabric marker or chalk to mark the creases' crossing point on the wrong side.
- Small scissors to trim the corner.
- Thread to match, and either the machine for an edgestitched finish or a hand needle for a slipstitched one.
How does a mitered corner work?
Fold a hem up along one edge and a hem up along the adjacent edge, and the two allowances overlap at the corner in a square block of four layers, with the raw end of one hem showing. A miter removes that block. When the corner of the fabric is folded in along the diagonal before the hems are folded, each hem edge now ends on that diagonal, and the two diagonal edges meet in a straight line from the inner corner to the outer point. The corner has at most two layers anywhere, and the raw edges are all enclosed. How to hem covers the double-fold hem that the miter is based on.
How do you sew a mitered corner, step by step?
These steps are for a double-fold hem of 1 cm turn-under plus 3 cm (1 1/4 in), on a square corner. The finished hem is 3 cm deep.
- Press the turn-under. Fold 1 cm (3/8 in) to the wrong side along both edges and press.
- Press the hem. Fold 3 cm (1 1/4 in) to the wrong side along both edges, over the turn-under, and press firmly. Two crease lines now cross near the corner.
- Unfold the second fold only on both edges, keeping the 1 cm turn-under pressed. Mark the point where the two 3 cm creases cross on the wrong side.
- Fold the corner in. Take the corner point and fold it diagonally to the wrong side, so the fold passes exactly through the marked crossing point and the two pressed crease lines lie on top of each other. The fold is at 45° to both edges. Press.
- Trim the corner. Unfold the flap, cut the triangle off 1 cm (3/8 in) outside the diagonal crease, and fold the trimmed edge in again along the crease. The raw diagonal edge will be enclosed under the hems.
- Refold the hems along the 3 cm creases. The two diagonal edges come together at the corner in a neat line from the inner corner to the point.
- Pin and stitch. Edgestitch along the inner fold of the hem, pivoting with the needle down at the inner corner, and either edgestitch along the diagonal as well or close it by hand with a slipstitch for an invisible finish.
How do you sew the miter closed from the inside?
For a corner that is clean on both sides, as on a tablecloth or a reversible apron, stitch the diagonal instead of folding it:
- Press the turn-under and the hem as in steps 1 and 2, then unfold both completely. The outer crease is the 1 cm line and the inner crease is the hem line, 4 cm (1 5/8 in) from the edge.
- Fold the corner of the fabric right sides together on the diagonal, so that the two raw edges lie on top of each other. The hem creases on the two edges now match.
- Draw a line at a right angle to the fold, from the point where the hem crease meets the fold to the point where it reaches the 1 cm crease. Stitch along it, backstitching at both ends, and stop at the 1 cm crease so the turn-under stays free.
- Trim the seam to 6 mm (1/4 in), press it open over the point of the ruler, and turn the corner right side out. Push the point out gently with a point turner.
- Refold the turn-under and the hem along the creases. The miter is seamed and sharp; edgestitch or slipstitch the hem.
On a deep hem of 5 cm (2 in) or more, this seamed version holds its shape through washing much better than the folded version.
Can you miter hems of different widths?
Yes. The fold through the crease crossing still works, but the diagonal is no longer at 45°: it runs from the crease crossing on the inside to the point where the two outer edges meet. Press the two different hems, unfold, mark the crossing, and fold the corner so the fold runs through the crossing and the creases on the folded flap continue the creases on the body. Trim, turn under and refold as before. This is how a 4 cm (1 5/8 in) hem on the bottom of a tunic meets a 1.5 cm (5/8 in) hem on its side slit, and how a wide tablecloth hem meets a narrower one on a runner.
Where are mitered corners used?
- Side slits on tops and tunics, where the bottom hem meets the slit's narrow hem.
- Napkins, tablecloths, runners and tea towels: every corner.
- Aprons and tote bags with turned hems rather than lined edges; sewing an apron uses mitered corners where the hem meets the sides.
- Envelope cushion covers, on the hem of the back opening where it meets the side; see sewing envelope cushion covers.
- Patch pockets with a hem, where the top hem meets the sides, though most are folded rather than mitered.
- Scarves and blankets with a self-hem.
What are the common mistakes with mitered corners?
- Folding the corner by eye instead of through the crease crossing. A miter that does not pass through the crossing leaves a gap or an overlap on the diagonal. Mark the point with chalk every time.
- Trimming too much. Leave a full 1 cm beyond the diagonal; a trimmed-flush corner frays into the hem.
- Not pressing between steps. Each fold depends on the last crease being sharp. A miter is pressed five times and sewn once.
- A blunt point comes from bulk inside the corner: trim the seam of a sewn miter to 6 mm and press it open before turning.
- Corners that will not match: the hems were pressed at different widths. Measure with a seam gauge rather than by eye on long edges.
- Mitering a bias or curved edge. The technique is for straight edges on grain; a curved hem is eased or faced instead, and a hem that crosses the bias stretches as you press.
When should you use a mitered corner instead of a folded one?
A plain folded corner, one hem over the other with the raw end tucked in, is fine on lightweight fabric with a narrow hem, where the extra layers hardly show. Miter when the hem is deeper than about 2 cm (3/4 in), the fabric is medium weight or heavier, or the corner will be seen from both sides. Where a hem meets a bound edge instead of another hem, the bias binding guide shows how to turn the binding at a corner, which is a miter in the binding rather than in the hem. If you sew the apron or the cushion cover from a Sewly pattern, the pieces include their allowances already; check the hem depth in the sewing guide before you press, and ask the guide if a step is unclear.