Fabric Quantity Calculator for Curtains & Drapery
Calculate exact fabric quantities for window treatments — enter your measurements, heading style and fullness required to get a precise cutting specification instantly.
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Cutting Specification
How to Use This Fabric Calculator
- Choose Metric or Imperial to set your working units for the whole calculation.
- Enter your window width (the overall structural opening) and finished drop, and choose whether you're measuring for a single panel or a pair.
- Set your stackback allowance (20–30%), or enter an actual track width if it's already installed.
- Choose your heading type and fullness level — the calculator will only allow fullness values realistic for that heading.
- Enter your fabric roll width and pattern repeat, if the fabric has one.
- Click Calculate for a full cutting specification: total fabric required, fabric widths needed, and cut length per drop.
Understanding Fullness, Stackback and Pattern Repeat
Fullness is how much fabric is used relative to the finished track width — a 2.0× fullness means the flat fabric is twice as wide as the track it hangs on, once gathered into folds. Higher fullness (2.5–3.0×) gives a richer, more luxurious drape, but uses proportionally more fabric.
Stackback is the extra track length, beyond the window itself, that lets curtains draw back fully off the glass when open. Without it, open curtains block part of the window even when fully drawn — 20–30% of the window width is standard practice.
Pattern repeat is the vertical distance before a printed or woven design repeats itself. When fabric has a repeat, extra length has to be added to each cut so the pattern lines up across joined widths, which increases the total fabric required beyond the plain calculation.
Worked Example: Fabric for a Pair of Curtains
Take a 150cm wide window, dressed as a pair with 25% stackback, standard 2.0× fullness, and a plain fabric on a 137cm roll. The recommended track width comes to 187.5cm (150cm × 1.25). Split across two panels, each needs 93.75cm of track width, which at 2.0× fullness means 187.5cm of flat fabric per panel — just over one fabric width, so two widths are needed per panel, four widths in total. For a 240cm floor-length drop with a double pencil pleat heading (9cm allowance) and the standard 1.5cm bottom hem, each cut length comes to 250.5cm. Four widths at that cut length gives 1,002cm of fabric — 10.1 metres once rounded up to a practical ordering quantity.
Frequently Asked Questions
How much fabric do I need for curtains?
It depends on your track width, fullness level, fabric roll width, drop, and heading type — there's no single fixed figure. Use the calculator above with your own measurements for an exact quantity, including pattern repeat and hem allowances.
What fullness level should I choose?
2.0× (Standard) gives a classic, tailored fold and uses the least fabric. 2.5× (Luxury) gives a fuller drape suited to most formal rooms. 3.0× (Premium) is the most opulent option, typically used with lightweight or sheer fabrics where the extra folds read as soft rather than bulky.
What's the difference between calculating for a single panel and a pair?
A pair splits the total track width across two panels that meet in the middle, each needing its own whole number of fabric widths — which is why a pair often needs more total fabric than a single panel of the same track width, once you round up each side separately.
How does pattern repeat affect the amount of fabric I need?
Every cut length is extended by one full pattern repeat, so that the design lines up correctly across joined fabric widths. A large pattern repeat on a short drop can noticeably increase the total fabric required compared to a plain fabric of the same width.
What is stackback and why does it matter?
Stackback is the amount of track that extends beyond the window opening so that open curtains clear the glass instead of covering part of it. It's typically 20–30% of the window width, and it directly increases the track width used in the rest of the calculation.