Pleat Calculator — Box, Knife & Inverted Pleats

As a rule of thumb, box pleats use 3× the finished width and inverted pleats (a box pleat reversed) also use 3×, because each pleat hides two folds of fabric behind the visible panel. Spaced knife pleats use about 2×. These ratios assume the hidden fold depth is about half the visible pleat width — deeper folds use more fabric. The precise figure is: knife pleat fabric = number × (visible width + 2 × fold depth); box pleat = number × (visible width + 4 × fold depth).

A box pleat has two folds that face away from each other, creating a flat panel on the outside with the excess fabric hidden behind. It uses the most fabric but gives a crisp, structured look.

Common pleat widths are 2.5–5cm (about 1–2in) for skirts, 5–8cm (about 2–3in) for kilts, and 1–2cm (about 0.4–0.8in) for fine pleating. The pleat width is the visible width on the outside of the garment.

Yes. Finished Width and Pleat Width each carry a unit button, so you can set them to inches (or other length units) and type imperial measurements directly. Both fields share one setting, and the finished width, the fabric width and the extra fabric in the results come back in the unit you chose, as does the pleat width in the copied job sheet. The pleat count is a ratio, so it is the same number either way.

A kick pleat is not handled by this calculator. It is a single short vent at a hem or seam (typically a 15–23cm / 6–9in opening with a small underlap of about 4–6cm), so it adds a fixed amount of fabric for the underlay rather than multiplying the whole panel width. Allow extra for the underlay piece plus seam allowances, not a fullness ratio.