Tools · Cutting
Every panel, cut to size, with the zip and piping figured — a printable cutting list for any box cushion.
Every panel is the finished size plus two seam allowances. The boxing (front and sides) cuts as one strip where the fabric width allows, otherwise as a front and two side panels with joining allowance. The back border is two half-height strips with 2 cm each for the zip placket, and the zip itself runs the cushion width plus 8 cm so it wraps the corners. Piping strips are straight-cut at 4 cm for standard 4–5 mm cord — on plain cloth, straight cut is fine for the straight runs of a box cushion; save bias for curves (see the piping & bias calculator). The layout estimate packs panels across the usable width; on patterned cloth, add roughly one repeat per row of panels — the calculator does this when a repeat is entered.
As a rule of thumb, a typical 55 x 55 x 10 cm seat cushion with piping takes about 1 to 1.2 metres of 140 cm plain fabric. The exact figure depends on size, fabric width and piping - the calculator produces a full cutting list and total for your measurements.
Cut every panel at the finished size plus two seam allowances: top and bottom panels at width + 2SA by depth + 2SA, the boxing strip at height + 2SA wide, and the zip border as two strips each half the height plus seam allowance plus about 2 cm for the zip placket.
The cushion width plus about 8 cm, so the zip wraps a little way around each back corner - this makes stuffing the cover far easier and lets the pad sit square.
Both the top and bottom seams are usually piped, so allow 4 x (width + depth) plus around 12 cm for joins - a 55 x 55 cushion takes about 4.5 metres.