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Category Household Calculators

Window Measurements

Unit System

Number of Windows

Window Opening Width

Window Opening Height

Mounting & Style

Mounting Type

Heading Style

Panel Configuration

Bottom Finish

Fabric & Allowances

Fabric Bolt Width

Pattern Repeat 0 = plain / no repeat

Side Extension Overlap beyond frame (per side)

Above Frame Distance Track/pole above frame top

Bottom Hem Allowance

Return Depth From pole face to wall (per side)

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About

Incorrect curtain measurements waste fabric and money. A curtain ordered 10cm too narrow exposes light gaps. One ordered without accounting for pattern repeat can require 30% more fabric than expected. This calculator computes the finished curtain width using the formula W_fabric = (W_window + 2 × S_overlap) × F_m, where F_m is the fullness multiplier determined by the heading style. It accounts for hems, headers, mounting offsets, return allowances, and pattern repeats across multiple fabric widths. Results assume standard residential windows with rigid or flexible track/pole systems.

Limitations: this tool does not account for fabric shrinkage after washing. Pre-wash or add 3 - 5% to the cut length for natural fibers. Sheer fabrics typically require a higher fullness multiplier (2.5× to 3×) than listed standard values. Always confirm measurements at three points across the window opening, as frames are rarely perfectly square.

Formulas

The total fabric width required for one window is computed as:

W_fabric = (W_window + 2 × S_overlap) × F_m + R_return + O_center

Where W_window = window opening width, S_overlap = side extension beyond the frame (typically 15cm per side), F_m = fullness multiplier for the chosen heading style, R_return = return depth on each side for wall clearance (typically 10cm × 2), and O_center = center overlap for paired curtains (typically 5cm).

The cut drop (height per panel) is:

H_cut = H_finished + A_header + A_hem + A_puddle

Where H_finished = desired finished length from track/pole to bottom edge, A_header = heading turn-up allowance, A_hem = bottom hem allowance (typically 15cm double-fold), and A_puddle = extra length for break or puddle effect.

The number of fabric widths needed is:

N_widths = ceil(W_fabricW_bolt)

Where W_bolt = usable fabric width from the bolt (typically 137cm or 54in). When a pattern repeat P_r exists, the adjusted cut per width becomes:

H_adj = ceil(H_cutP_r) × P_r

Total fabric length = N_widths × H_adj. Track or pole length = W_window + 2 × S_overlap. Bracket count = ceil(track length ÷ 60cm) + 1.

Reference Data

Heading Style	Fullness Multiplier	Header Allowance	Best For	Typical Hook Spacing
Flat / Plain	1.0×	5cm	Modern, minimal rooms	10cm
Pencil Pleat	1.5×	8cm	Traditional, versatile	6cm
Pinch Pleat (Triple)	2.0×	10cm	Formal, heavy fabrics	12cm
Goblet Pleat	2.5×	12cm	Luxury, tall windows	15cm
Ripple / Wave Fold	2.0×	8cm	Contemporary, S-fold tracks	8cm
Eyelet / Grommet	1.5×	4cm	Casual, poles only	15cm
Rod Pocket	2.0×	6cm	Sheers, café curtains	N/A (continuous)
Tab Top	1.5×	5cm	Casual, decorative poles	15cm
Box Pleat	2.5×	10cm	Valances, formal	10cm
Cartridge Pleat	2.0×	10cm	Heavy lined draperies	12cm
Inverted Pleat	2.0×	10cm	Tailored, clean lines	12cm
Gathered (Standard)	2.0×	8cm	Cottage, traditional	8cm

Frequently Asked Questions

The fullness multiplier directly scales the total fabric width. A pinch pleat at 2.0× requires double the flat-panel width. For a 200cm window, that is 460cm of gathered fabric versus 230cm for a flat panel (including side overlaps). Higher fullness means more fabric widths from the bolt, which compounds when a pattern repeat is involved. Switching from pencil pleat (1.5×) to goblet (2.5×) on a large window can increase fabric cost by 60 - 70%.

Pattern repeat alignment is critical for multi-width curtains. If your fabric has a 64cm vertical repeat and your cut drop is 250cm, each width must be cut at 256cm (4 × 64) to ensure the motif aligns at the seam. Ignoring this wastes at least one repeat length per additional width and produces visually mismatched panels.

Standard practice is 1cm clearance above the floor for functional curtains that open and close daily. A "break" adds 2 - 5cm of extra length for a slight fold at the floor. A "puddle" adds 10 - 20cm for a dramatic pool of fabric. Puddle styles are not recommended for high-traffic areas or homes with pets.

For wall-mounted brackets, measure from the bracket hook point (typically 10 - 20cm above the window frame) to the desired bottom edge. For ceiling-mounted tracks, measure from the ceiling down. The calculator adjusts the finished drop accordingly. Ceiling mounts create the illusion of taller windows and eliminate the visible bracket gap above the heading.

The industry standard is one bracket every 60cm, plus one at each end. For a 240cm track: ceil(240 ÷ 60) + 1 = 5 brackets. Heavy fabrics like velvet or triple-pleat lined draperies may require brackets every 40 - 50cm to prevent track sag.

The return is the distance from the front face of the track or pole back to the wall. It prevents light leakage at the sides. Standard return depth is 10cm per side for single tracks and 15cm for double tracks (sheers behind main curtains). Omitting the return creates visible light gaps at the bracket points, especially problematic in bedrooms requiring blackout.

Standard decorator fabric comes in 137cm (54in) wide bolts. Some sheers are 300cm wide (railroaded). If your total fabric width after fullness is 400cm and bolt width is 137cm, you need 3 fabric widths, which means 2 vertical seams. Wider bolt widths reduce seams but limit fabric choices.