Curtain Size Calculator

Curtain fabric estimation requires measuring window width and desired drop length, then accounting for fullness ratio (how gathered the curtain is), hem allowances, and header allowances. Getting this right ensures curtains look full and luxurious rather than flat and underfed.

Fabric Width Required formula: Total Fabric Width = Window Width × Fullness Ratio × Number of Panels

Fabric Length Required per Panel: Cut Length = Finished Drop + Top Hem Allowance + Bottom Hem Allowance + Pattern Repeat

What each variable means:

• Window Width — measure the pole or track width, not just the window opening; for a full look, the pole should extend 15–30 cm beyond each side of the window
• Fullness Ratio — how much fabric width relative to the window width; standard is 2.0× to 2.5× for a full look; sheer panels may use 3× for a floaty effect; tab-top panels may use 1.5×
• Finished Drop — from pole to where the curtain should end: 1–2 cm above floor for a modern look; touching the floor for an elegant look; 15–25 cm puddle on the floor for a dramatic romantic style
• Top Hem — typically 8–15 cm for a rod pocket or pinch pleat header; 4 cm for eyelet/grommet (reinforced by the ring)
• Bottom Hem — typically 10–15 cm for a weighted, professional finish
• Pattern Repeat — vertical distance of any fabric pattern; each panel must start at the same point in the repeat for alignment

Worked example: Window 180 cm wide. Desired drop: 250 cm (floor length). Two panels, 2.5× fullness. Pattern repeat: 30 cm.

Total fabric width = 180 × 2.5 = 450 cm; two panels → each panel 225 cm wide Cut length = 250 + 12 (top) + 12 (bottom) + 30 (pattern) = 304 cm per panel

Total fabric ordered = 2 panels × 225 cm wide — buy 225 cm width or wider fabric. Yardage = 2 panels × 304 cm = 608 cm = 6.08 meters (order 6.5 m to have margin)

Lining note: Interlining or blackout lining is cut the same width but 10 cm shorter than the face fabric (no pattern matching needed for lining).