Pattern piece E
Pleat calculator
Knife, box and inverted box pleats: how much fabric they take, how deep and how far apart they are, where to mark every fold, and how much to buy for a pleated skirt.
- Fabric width to cut
- 85 1/4 in216.5 cm with end allowances
- Pleat depth
- 2 in14 pleats, 2 × depth each
- Spacing
- 2 inpleat to pleat, finished
- Fabric to buy
- 1 1/2 yd2 widths × 26 5/8 in
Knife pleats take up 56 in of extra fabric: 3 times the finished 28 in.
Full knife pleats: each depth equals the spacing, so the pleated edge is three layers thick and uses three times its length.
Over the hips the pleats open to about 1 9/16 in deep each, so stitch them down only from the waist to the high hip, or taper them.
Marking guide: 14 pleats
| Pleat | Lines |
|---|---|
| 1 | place 5/8 in · fold 4 5/8 in |
| 2 | place 6 5/8 in · fold 10 5/8 in |
| 3 | place 12 5/8 in · fold 16 5/8 in |
| 4 | place 18 5/8 in · fold 22 5/8 in |
| 5 | place 24 5/8 in · fold 28 5/8 in |
| 6 | place 30 5/8 in · fold 34 5/8 in |
| 7 | place 36 5/8 in · fold 40 5/8 in |
| 8 | place 42 5/8 in · fold 46 5/8 in |
| 9 | place 48 5/8 in · fold 52 5/8 in |
| 10 | place 54 5/8 in · fold 58 5/8 in |
| 11 | place 60 5/8 in · fold 64 5/8 in |
| 12 | place 66 5/8 in · fold 70 5/8 in |
| 13 | place 72 5/8 in · fold 76 5/8 in |
| 14 | place 78 5/8 in · fold 82 5/8 in |
For a skirt, cut 2 widths of 44 in fabric, each 26 5/8 in long, and join them; place each join in the back fold of a pleat so it never shows. Buy 1 1/2 yd (1.4 m).
How the pleat calculator works
Every fold of a pleat hides fabric: it goes back by the depth and comes forward again, so each fold takes twice the depth. A knife pleat is one fold, all facing the same way. A box pleat is two folds turned away from each other, with the hidden fabric behind the box; an inverted box pleat is the same two folds turned toward each other, meeting at the front. Box and inverted pleats therefore take four times the depth each. Fabric needed = finished length + number of pleats × 2 or 4 × depth, plus a seam allowance at each end.
Choose what to work out. Fabric needs the number of pleats and their depth. Depth shares out the fabric width you already have. How many fits as many pleats of your depth as that fabric allows. The spacing is always the pleated length divided by the number of pleats; leave flat sections at the ends in the extra settings, for example either side of a zip.
Full pleats are pleats whose folds meet behind: for knife pleats the depth equals the spacing, for box pleats it is half the box width. They give three layers at the edge and need three times the finished length. Deeper pleats overlap more; shallower ones look lighter.
Worked example: a 28 in waist with 14 knife pleats gives a 2 in spacing. Full pleats 2 in deep need 28 + 14 × 2 × 2 = 84 in, plus two ⅝ in allowances: 85¼ in of fabric width. Over 40 in hips (with ease) the pleats open to about 1½ in deep, so stitch them down only to the high hip.
Mark the lines from the left cut edge: fold on each solid line and bring the fold over to its dashed line in the direction of the arrow, then pin or baste across the top.
Sources
- The fabric, depth and spacing figures are the geometry above, worked out in your browser; nothing is estimated.
- New Mexico State University, Making Perfect Garment Hems (Guide C-314): hems on straighter edges are 2 to 3 in (5 to 7.5 cm) deep, the reason for the 2 in default here.
- New Mexico State University, Clothing Construction Standards (Guide C-214): pleats uniform in width unless the design varies.
Questions
How much fabric do I need for a pleated skirt?
For full knife or box pleats, about three times the waist plus the seam allowances, cut as several fabric widths joined together. Enter your skirt length and fabric width to see how many widths that is and how much to buy.
What is the difference between box and inverted box pleats?
They are the same folds seen from opposite sides. A box pleat shows a flat panel standing out with its folds turned under; an inverted pleat shows two folds meeting in a line, with the panel hidden behind. Both take four times the depth.
Where do I hide the joins between fabric widths?
Put each seam in the back fold of a pleat, where the fabric turns behind the face. Plan it with the marking guide before joining, then adjust a flat end slightly if a seam lands on a visible face.
My pleats spread open at the hips. What can I do?
Check the hip figure: if the flat fabric is only a little wider than your hips, the pleats must open to go round. Use more fabric or more pleats, or stitch the pleats down from the waist to just above the fullest part so they open below it.