⚡ Quick Answer: Sewing a Mitered Corner
A mitered corner is a 45 degree seam that joins two folded hems. Press both hems round the napkin, fold each corner diagonally so the two hem folds meet, sew down the diagonal, cut the wedge of waste away, then turn the corner out and press. The point comes out sharp because the seam, not the folding, is what holds it square.
A napkin hem is a rectangle of fabric folded twice on every side, and four corners where those folds have to meet. A plain overlap at the corner leaves a lump. A miter cuts the lump away and joins the folds at an angle, so all four corners come out flat, square and identical.
The method below is written around the two things people actually get wrong: the cut size and the stitch line. Every other step is pressing, and pressing is the part that cannot be rushed.
What a Mitered Corner Actually Is
Look at the back of a finished napkin corner and you can see the shape: a small triangle of seam allowance, the two hem folds meeting it at 45 degrees, and no fabric doubled over itself anywhere.
The miter works because the two hems are pressed before the corner is sewn. The creases give you the line to sew along. You are not measuring the corner, you are joining two creases that already exist.
Two other corner finishes get confused with this one. A folded corner simply folds the excess in and presses it, which is quick and produces bulk. A bound corner wraps bias tape round the edge, which is a different project, though the reversible table runner shows the same mitre used on a long edge. The miter is the only one that gives a flat, sharp point with the hem running unbroken round all four sides.
The creases do the measuring. If you find yourself measuring the corner with a ruler, the hems are not pressed sharply enough.
Work Out the Cut Size Before You Cut
Every corner in this article depends on one number: how much fabric each hem turn takes.
A hem is turned twice so the raw edge is hidden. If you turn half an inch and then half an inch again, each side of the napkin uses one inch of fabric, and the cut square is two inches bigger than the finished square. That is the whole calculation.
| Finished size | Turns | Cut size |
|---|---|---|
| Cocktail, 6 x 6 in | 1/2 in and 1/2 in | 8 x 8 in |
| Tea, 12 x 12 in | 1/2 in and 1/2 in | 14 x 14 in |
| Lunch, 14 x 14 in | 1/2 in and 1/2 in | 16 x 16 in |
| Dinner, 20 x 20 in | 1/2 in and 1/2 in | 22 x 22 in |
| Formal, 22 x 22 in | 1/2 in and 1 in | 25 x 25 in |
The formal size uses an uneven turn on purpose. A wide hem reads as table linen, and the extra inch gives the corner enough material to press flat without the point going soft.
Cut on the grain, not around a print. A square cut half an inch out of true will look like a badly sewn napkin no matter how good the corners are.
Get the Square Actually Square
Fabric off the bolt is rarely square. It is pulled on the roll, and the cut edge you buy is often a centimetre away from a right angle to the selvedge.
Pull a thread to find the true crosswise line, then cut along the gap it leaves. It is slower than eye and it takes about a minute per napkin. Once you have one true edge, fold the fabric and use it to square the others.
Check the finished square corner to corner. Both diagonals should measure the same. If one is longer, the square is a parallelogram, and the hem will pull one way round the napkin.
Press with a little starch or sizing before the first fold. A crisp hem presses itself, and every later step is easier because the creases hold where you put them.
What You Need
The list is short, and two items are the difference between even hems and hems that wander.
| Item | Why it matters |
|---|---|
| Cotton or linen, washed and pressed | Shrinkage happens once, and it should happen before you cut |
| Hem gauge or seam gauge | Sets the same turn on every side without measuring twice |
| Quilting ruler and rotary cutter | A true square in one pass, no scissors drift |
| Iron with a firm press | The creases are the pattern for every corner |
| All purpose polyester or cotton thread | Match the fibre of the fabric where you can |
| Universal needle, 80/10 | Heavy enough for linen, fine enough not to mark cotton |
| Glass head pins or clips | Holds the mitre while it goes under the needle |
Pre-wash the fabric, dry it and press it before anything else. Cotton can move three to five percent in the first wash, and a napkin that was square when you sewed it will not be square after the first dinner party if you skip this.
Step 1: Press the First Turn
Set the hem gauge to your first turn, half an inch in most cases. Fold the edge over the gauge, press, and move along the side in short sections rather than trying to fold the whole length at once.
Work all four sides before you go back to any of them. The corners stay raw and unfolded at this stage, and that is correct: you cannot miter a corner until both turns are pressed.
Press on the right side as well as the wrong side for the last few seconds. The crease reads better from the right side, and the visible line is what you will follow when you topstitch.
Step 2: Press the Second Turn and Mark the Corner
Turn the edge again by the same amount, or by your chosen second amount if the hem is uneven, and press. You now have a hem of twice the turn width with a clean folded edge.
The corner is a small square of double thickness, and the two hems cross inside it. Find the point where the fold lines cross and mark it lightly with a pin or a chalk dot. It sits in from the corner by about twice the hem width.
Do the same at the other three corners before you sew anything. The same pressing rhythm carries over to a bargello table runner when you are ready for a bigger piece. Doing all four at once keeps your hand in and stops the second corner being cut differently from the first.
Step 3: Fold the Corner and Find the Stitch Line
Open the hems at one corner, then fold the corner diagonally with the right sides together, matching the two pressed fold lines exactly. The folded edge that results is your diagonal.
Lay a ruler along that fold and look for the point where the raw edge of the hem meets it. Mark a line perpendicular to the diagonal at that point. That line is where you sew.
Sew slightly inside the crossing point, not at the very corner. A stitch line set a hair too far out is what makes a mitered corner stand up and refuse to press flat.
Mark all four corners at the same time and compare them. They should be identical in length and angle, and any that is not is worth re-folding before the machine comes out.
Step 4: Sew the Corner and Cut the Wedge
Sew along the marked line with a normal straight stitch, length around 2.5 mm, and backstitch at both ends. A miter seam is short and takes a lot of load when the corner is turned, so those few backward stitches are what keeps it from opening.
Cut the excess fabric away leaving about a 6 mm seam allowance. Cut on a slight angle so the remaining allowance is narrowest at the point, which is where the bulk would otherwise gather.
Do not cut into the stitching. Once the allowance is cut, the corner cannot be repaired without unpicking the whole hem, so cut slowly with the points of small sharp scissors.
Step 5: Turn, Point and Press
Turn the corner right side out through the opening you cut. Push the point out from the inside with a point turner, the blunt end of a pencil or a knitting needle, never with scissors.
Finger press the corner seam open first, then press the corner with the iron. Pressing the seam open before the corner is flattened is what lets the miter sit flat instead of bulging.
Press the hem back into place along every side and check that the fold lines still line up with the creases. If one side has shifted, the second turn was pressed too loosely and the hem will not stay put in the wash.
Step 6: Topstitch the Hem
Topstitch close to the inner fold of the hem, around 3 mm in, using the same straight stitch. Start in the middle of one side so the overlap where you finish is not sitting at a corner.
Slow down as you approach each corner and stop with the needle down exactly at the corner seam. Lift the presser foot, pivot the napkin 90 degrees, lower the foot and carry on. A pivot one stitch early leaves a notch, one stitch late leaves a loop.
At the end, overlap four or five stitches, backstitch and pull the thread tails to the back with a needle. Do not leave them hanging at the corner where they will fray in the wash.
Why Corners Stand Up, and How to Fix One
The most common complaint about this method is a corner that folds over on itself instead of lying flat. It is almost never the pressing. It is the stitch line or the trim.
| Problem | Cause | Fix |
|---|---|---|
| Corner stands up or folds over itself | Stitch line set too far out from the crossing point | Unpick the corner seam and re-sew slightly inside the crossing |
| Lumpy, bulky corner | Too much allowance left when the wedge was cut | Trim to about 6 mm, tapering the allowance towards the point |
| Point is rounded, not sharp | Corner pushed out with something sharp, or not pressed | Re-wet the point, shape it from inside, press until dry |
| One corner different from the rest | Marked separately instead of at the same time as the others | Mark all four, compare them, re-fold any that differ |
The same unpick and redo rule applies to any seam you are unhappy with, as in the French seam guide. If a corner has already been topstitched and is wrong, unpick the corner seam and the topstitching for about 5 cm either side, then redo it. It takes ten minutes. Starting the whole napkin again takes an hour.
Hem Widths and Fabric Choice
Hem width is a style decision with one practical limit: the miter needs the two turns to total at least 1.5 cm or the corner becomes fiddly and the point loses definition.
| Fabric | Suggested turns | Result |
|---|---|---|
| Quilting cotton, prints | 1/2 in and 1/2 in | Light, crisp, everyday napkin |
| Cotton lawn or voile | 1/4 in and 1/4 in | Fine hem for a delicate napkin, hardest to miter |
| Midweight linen | 1/2 in and 1 in | Wide hem, formal look, presses beautifully |
| Linen cotton blend | 1/2 in and 1/2 in | Best balance of drape and an easy miter |
Wash and press linen hot, and press cotton with steam. Linen softens with every wash, so a stiff new napkin is not the fault of your hem. Sew with a fresh needle and a stitch length of 2.5 mm, and test on a scrap of the same fabric before the first corner.
Making a Set: Sizes and Yardage
Cut everything before you sew anything. Cutting is where the mistakes are, and a stack of true squares sewn in one sitting gives a matching set.
| Set of four | Cut size | Fabric needed |
|---|---|---|
| Cocktail, 6 x 6 in | 8 x 8 in | Half a metre |
| Lunch, 14 x 14 in | 16 x 16 in | One metre |
| Dinner, 20 x 20 in | 22 x 22 in | One and a half metres |
| Formal, 22 x 22 in | 25 x 25 in | Two metres |
On a 112 cm wide fabric you can fit four 22 inch squares across with room for the turn, which is why one and a half metres is the usual amount for a dinner set. Buy the same dye lot for all four, and buy a little extra if the print has a large repeat you want to centre.
Frequently Asked Questions
How much fabric do I need for a mitered corner napkin?
The cut square is the finished size plus the two hem turns on each side. For a 20 inch dinner napkin with half inch turns, the cut square is 22 inches, and four of them take about one and a half metres of 112 cm fabric.
What size hem should a cloth napkin have?
Half an inch for everyday cotton, and half an inch then one inch for a wide formal hem on linen. The two turns should total at least 1.5 cm so the corner has enough material to press flat.
Why does my mitered corner stand up instead of lying flat?
The stitch line was set too far out from the crossing point, or too much allowance was left when the wedge was cut. Unpick the corner seam and re-sew slightly inside the crossing, trimming the allowance to about 6 mm and tapering it towards the point.
Can I sew mitered corners without a point turner?
Yes. Use the blunt end of a pencil, a knitting needle or a closed pair of embroidery scissors. Never use a sharp point, because it pushes through the weave and the hole does not close up after washing.
Should I topstitch the hem after mitering the corners?
Yes. Topstitching about 3 mm from the inner fold secures the hem, keeps the mitre in place and stops the hem rolling in the wash. Start in the middle of a side so the overlap is not at a corner.
Do I need to pre-wash fabric before making napkins?
Cotton and linen can shrink three to five percent in the first wash. Pre-wash, dry and press before cutting, or the napkin will not stay the size you planned.
What is the difference between a mitered corner and a folded corner?
A folded corner turns the excess fabric under and presses it, which leaves bulk. A mitered corner sews a diagonal seam across the corner, cuts the waste away and turns it out, so the hem runs unbroken and the point stays flat.
Can I make mitered corner napkins with a reversible or double sided finish?
Yes. Cut two squares, sew them right sides together leaving a turning gap, clip the corners and turn through. It is a different corner than the miter in this article and it is faster, but the finished edge is a seam rather than a hem.
Conclusion
The miter comes down to three decisions: cut the square true, press both turns before the corner, and set the stitch line slightly inside the crossing point. Get those right and the corner turns flat every time.
If a corner will not lie down, unpick it rather than fight it. The table above names the cause, and every cause is a decision you can change on the next napkin instead of the whole set.
Are you making a set for your own table or as a gift, and which fabric did you pick?
About This Guide
Written by Mithu, who sews table linen by the dozen and has learned that the iron, not the machine, decides whether a corner sits flat.
The sizes and cut sizes here follow the standard table linen proportions used by sewing teachers, and the tolerance for turns and trimming is the one that holds up in a domestic wash. Test the corner on a scrap of your own fabric before you commit a set.
All images in this article were created using AI.