About

This tool is designed for professional seamstresses and serious DIY enthusiasts who require exact fabric estimates for window treatments. Unlike basic calculators, this engine accounts for Pattern Repeats, ensuring that prints align perfectly across joined panels - a critical detail often missed, resulting in mismatched curtains or fabric shortages.

The calculator determines the Number of Widths required based on your chosen Heading Style (which dictates the Fullness Ratio) and automatically rounds up vertical cuts to the nearest full pattern repeat. This method, known as Pattern Matching, guarantees that the design flow remains uninterrupted across the entire window width.

Formulas

The core logic separates the horizontal coverage from the vertical cut length, ensuring pattern alignment.

{

Widths Required N = ⌈ W_track × R_fullnessW_fabric ⌉Raw Cut Length L_raw = H_drop + A_head + A_hem

If a pattern exists (P_repeat > 0), the cut length is adjusted to round up to the next full repeat:

L_final = ⌈ L_rawP_repeat ⌉ × P_repeat

Total Fabric T = N × L_final

Reference Data

Heading Style	Fullness Ratio	Description
Pencil Pleat	2.0 - 2.5	Tightly gathered folds. Standard choice for tracks.
Triple Pinch Pleat	2.5 - 3.0	Formal, decorative permanent pleats. High fabric usage.
Eyelet / Grommet	1.8 - 2.2	Modern metal rings. Requires less fullness but specific pole hardware.
Tab Top	1.5 - 2.0	Fabric loops. Casual look, lowest fabric consumption.
Wave / Ripplefold	2.2 - 2.5	Structured, sinuous curves. Requires specific tracks and tapes.
Goblet Pleat	2.5 - 3.0	Cylindrical heading, stuffed to maintain shape. Luxurious.
Box Pleat	2.5 - 3.0	Tailored, flat folds. Very formal.

Frequently Asked Questions

Professional curtains are cut so that the pattern starts at the exact same point on every panel (usually the top). This ensures that when panels are sewn together, the pattern continues seamlessly horizontally. We calculate how many full vertical repeats fit your required drop and round up, so you have enough fabric to align the pattern.

Measure the full width of your curtain pole or track, not the window itself. If you have a pole, exclude the finials (decorative ends). If you have an overlap arm on a track, include that in the width to ensure curtains overlap correctly in the middle.

Standard fabric comes off the roll vertically (up the roll). Railroading means turning the fabric 90 degrees and running it horizontally. This is common for wide windows to avoid seams, but requires fabric that is wide enough to cover the drop (usually 280cm+). This calculator assumes standard vertical orientation.

Yes. Natural fibers like cotton, linen, and viscose can shrink 5-10% after the first wash or dry clean. It is best practice to buy 10% extra and pre-wash the fabric, or add 5-10% to the hem allowance in the calculator settings.