Curtain & Pleat Fabric Calculator

Frequently Asked Questions

How much flat fabric do pleated curtains need?

Flat width = window width × fullness ratio + returns + side hems. For a 60 in window with 2× fullness, 3 in returns each side and 1.5 in side hems: 60 × 2 + 6 + 3 = 129 in of fabric across the pair (or per panel for a single).

What fullness ratio should I use?

Sheers and lightweight fabrics: 2.5–3× window width for soft drape. Medium drapery: 2–2.5×. Heavy or pinch-pleat: 2× is plenty. Less than 2× looks skimpy when closed.

How long should I cut each panel?

Drop = finished length + top hem/header + bottom hem. A 96 in finished panel with a 4 in header and 4 in double-fold bottom hem needs 96 + 4 + 8 = 108 in of fabric length, plus a pattern repeat allowance if any.

How do I account for a pattern repeat?

Round each cut length up to the next multiple of the pattern repeat so panels match. A 27 in repeat on a 108 in cut becomes ceiling(108 ÷ 27) × 27 = 108 in - round to 135 in if the repeat does not divide evenly.

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How This Calculator Works

The single biggest mistake in making curtains is buying fabric for the window's width instead of the much greater width a proper heading demands. A curtain only looks rich and full because its flat fabric width is one-and-a-half to two-and-a-half times the track it covers - that multiplier is the fullness ratio, and it differs by heading style: a simple gathered rod-pocket needs about 1.5×, a pencil pleat 2 to 2.25×, and a pinch or goblet pleat around 2.5×. This calculator takes the window or track width, the chosen heading, the number of panels, and the side hems and returns (the bit that wraps back to the wall to block side light), and computes the total flat width of fabric required. It then works out how many fabric "widths" (drops) you must seam together at the bolt width you are buying, adds the top and bottom hem allowances to the finished drop to get the cut length, and returns the total fabric in yards and metres rounded up - so you order enough to gather, not a flat sheet that hangs limp.

Formula / Method

Flat width = window width × fullness ratio + (panels × 2 × side hem) + 2 × return depth. The fullness multiplier comes from the heading style; side hems are doubled because every panel has two sides; returns are added once per outer edge that wraps to the wall. Widths needed = ceil(flat width ÷ fabric bolt width) - you must round up and seam, because part of a width still needs a whole cut. Cut drop = finished drop + top hem (heading turn-down and tape) + bottom hem (a deep double hem for weight). Total length = widths needed × cut drop; yards = inches ÷ 36 rounded up to the next ⅛, metres rounded up to 0.1. Centimetre inputs convert internally (÷2.54) and results convert back. Window width, drop, bolt width, and panels must be positive, hems non-negative, or the calculation is skipped so it never returns NaN.

Worked Example

A 60-inch window, 84-inch finished drop, pinch-pleat heading (fullness 2.5), 2 panels, 1½-inch side hems, 3-inch returns, 8-inch top and bottom hems, on 54-inch fabric. Flat width = 60 × 2.5 + (2 × 2 × 1.5) + (2 × 3) = 150 + 6 + 6 = 162 inches. Widths needed = ceil(162 ÷ 54) = 3. Cut drop = 84 + 8 + 8 = 100 inches. Total length = 3 × 100 = 300 inches ≈ 8.333 → 8.375 yards (about 7.7 m). Drop the heading to a simple rod pocket (fullness 1.5) and the flat width falls to 60 × 1.5 + 12 = 102 inches, only 2 widths - the heading choice alone changed the fabric bill by a third.

Common Mistakes

Buying fabric equal to the window width and ending with flat, skimpy curtains that will not gather or pleat.

Forgetting the return - the curtain then stops at the bracket and side light leaks around the edge.

Skimping the top hem so there is not enough turn-down to attach heading tape or hooks cleanly.

Using a single bottom hem; curtains want a deep double hem for weight and a straight hang, which adds inches to the cut drop.

Ignoring pattern repeat - matching a print across seamed widths adds up to one full repeat per extra width on top of this figure.

Tips & FAQ

What fullness should I choose? 1.5× reads as gently gathered, 2× as full, 2.5× as luxurious; sheers often go 2.5–3× because the fabric is light and wants extra body. How deep a top and bottom hem? A typical heading turn-down plus tape is 4–8 inches, and a weighted double bottom hem is often 4 inches doubled (8 inches of fabric) - check your heading tape's instructions. Do I always round widths up? Yes; a partial width still requires a full cut and a seam, so the bolt purchase is always whole widths. What about pattern repeat? Add one repeat per additional seamed width so the motif lines up across the curtain - this tool sizes plain fabric; add the repeat allowance separately. Lining? Lining is a separate, slightly narrower cut at the same drop; size it once the fashion-fabric widths are known. Two panels or one? A pair that draws to the centre needs the side hems counted on both panels, which this tool does via the panel count - a single fixed panel changes only that term.

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