Curtain & Window Treatment Calculator
Measure your window, pick a style and fullness, and we'll calculate exactly how much fabric to buy — including lining and pattern repeat adjustments.
Measure the full rod or track width, including any overhang past the window frame.
From the rod or track to where you want the curtain to end (sill, below sill, or floor).
How the curtain splits across the window.
Double-fold hem — typically 4–8" / 10–20 cm.
If your fabric has a repeating motif, enter the repeat distance.
Fullness ratios explained
The fullness ratio determines how much fabric gathers across the rod relative to the window width. A 2× ratio means you use twice the window width in fabric — the standard for most curtains that look “full” when closed and stack neatly when open.
1.5× (standard) works for flat panels, tab tops, and casual rooms where you want a relaxed, slightly rippled look. 2× (full) is the go-to for rod pocket and grommet curtains in living rooms and bedrooms. 2.5× (luxe) suits pinch pleats and formal dining rooms. 3× (sheer) is reserved for voiles, sheers, and layered treatments where you want clouds of fabric.
Fabric weight matters: lightweight sheers can handle 3× without looking heavy, while a thick velvet at 3× will overwhelm the rod and bunch awkwardly. Match the ratio to both the style and the fabric.
Header styles
Rod pocket— a sewn channel (casing) at the top through which the rod slides. Creates soft, uniform gathers. Best for stationary or seldom-opened curtains because the fabric grips the rod when you push it.
Grommet (eyelet)— metal rings punched through a reinforced header. The rod threads through the rings, creating deep, even S-folds. Easy to open and close. Requires interfacing (also called interlining or Vilene) or buckram behind the header for stability.
Tab top— fabric loops sewn at even intervals along the top edge. The rod is visible between tabs, giving a casual, cottage-style look. Tabs can be buttoned, knotted, or tied for variation. No extra header allowance is needed.
Pinch pleat— the most tailored style. Fabric is folded into groups of two or three pleats (French pleat, goblet pleat, or cartridge pleat) and stitched at the base. Requires stiff buckram or crinoline in the header and usually attaches to a traverse rod with drapery hooks.
Why add lining?
Lining protects the face fabric from UV damage, which causes colors to fade unevenly — especially on south- and west-facing windows. A standard cotton sateen lining adds years of life to your curtains.
Lined curtains drape better because the extra layer adds body and weight, keeping folds smooth and preventing the face fabric from clinging or floating. They also block more light and provide a thin layer of thermal insulation.
For blackout needs, use a three-pass blackout lining (white/black/white layers) instead of standard sateen. For thermal control, interlining with bump cloth or domette flannel between the face and lining creates a luxurious, padded curtain that insulates windows effectively.
Measuring your window
Width:Measure the rod or track, not the window glass. Most rods extend 3–6" (8–15 cm) past each side of the window frame so that curtains stack off the glass when open. Include this overhang in your width measurement.
Height: Measure from the rod (or the bottom of the rings, for grommet and pinch-pleat styles) down to your desired endpoint. Common endpoints: sill length (just above the sill), below sill (4–6" below), floor length (half an inch above the floor), or puddle(fabric pools 2–4" on the floor for a romantic look).
Always use a steel tape measure — cloth tapes stretch. Measure in at least three spots across the width (windows are rarely perfectly square) and use the widest measurement. For height, measure at both sides and the center, and use the longest measurement.