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Curtain Fabric Calculator — How Much Fabric Do You Need? (+ Reference Charts)

Calculate exactly how much curtain fabric to buy per window. Window width × fullness multiplier + seam and hem allowances. Result in cm and linear meters — with fullness and heading reference tables.

🗓️ Updated June 2026 Reviewed by Martín Rodríguez

Calculator Free · Private

Reviewed by: Martín Rodríguez (editorial policy ) · Last reviewed: Jun 20, 2026

Rod / Track Width*

Drop (Curtain Length)*

Fullness Multiplier*

Heading Style*

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This calculator tells you exactly how much fabric to buy for curtains on a single window, using the professional sewing formula: Fabric Width = Window Width × Fullness Multiplier + 20 cm (side seam allowances), and Fabric Length = Drop + Top Header Allowance + 20 cm (double bottom hem). The fullness multiplier varies by heading style: 2× for standard gathered curtains, 2.5× for pencil-pleat tape or voile, 1.5× for eyelet/grommet panels, up to 3× for ultra-full sheer voile.

When to use this calculator

Buying fabric at a store for a DIY sewing project — knowing the exact centimeters and panels prevents buying too little or wasting money on excess yardage.
Quoting material costs for a home-renovation or interior-design client who needs curtains on multiple windows with different widths and drop lengths.
Planning blackout or thermal curtains where heavy fabric is expensive and precise measurement directly controls project budget.
Ordering patterned fabric online where pattern repeat adds extra length — use the base calculator first, then add one full repeat per panel.

Heading Style: Fullness Multiplier & Header Allowance Reference

Heading Style	Fullness Multiplier	Header Allowance (cm)	Visual Effect
Eyelet / Grommet	1.5×	5 cm	Minimal gather, modern look
Rod Pocket (standard)	2×	8 cm	Classic soft folds (recommended)
Pencil-Pleat Tape / Voile	2.5×	10 cm	Fuller, more voluminous
Pinch-Pleat Hooks	2×	12 cm	Structured pleats
Extra-Full Sheer Voile	3×	10 cm	Maximum fullness, very light fabric

Fuente: Cotswold Sewing School — Calculating Fabric for Curtains (2022); Direct Fabrics — Curtain Fabric Calculator Guide

How it works

How It Is Calculated

The calculator applies the standard curtain-fabric formula used by professional seamstresses and window-treatment workrooms worldwide:

Fabric Width Needed

Fabric Width (cm) = Window Rod Width × Fullness Multiplier + 20

Rod/Track Width — the width of the curtain rod or track, end to end. Rods are typically 15–30 cm wider than the window frame so the open curtain doesn't block light.

Fullness Multiplier — the ratio that creates gathers. 2× is the professional standard for a classic gathered look. Sheer voile uses 2.5×–3×. Flat eyelet panels use 1.5×.

+20 cm — 10 cm double-fold side hem on each side (left and right), the standard side-seam allowance.

Fabric Length Needed

Fabric Length (cm) = Drop + Header Allowance + 20

Drop — from the bottom of the rod or ring down to the desired finish (floor level, sill, or below sill). Measure from the rod, not from the window frame.

Header Allowance — fabric needed for the top heading (varies by style, see table below).

+20 cm — a double 10 cm bottom hem, folded twice to add weight and give a crisp professional finish.

Converting to Linear Meters

Fabric is sold on rolls (bolts). The most common width is 140 cm; blackout and wide voile often come on 280 cm rolls.

Panels needed  = ⌈ Fabric Width ÷ Roll Width ⌉   (always round UP)
Linear meters  = Panels × Fabric Length ÷ 100

Fullness Multiplier Reference Table

Style	Multiplier	Visual effect
Flat panel / eyelet	1.5×	Minimal gather, modern look
Standard gathered	2×	Classic soft folds (recommended)
Pencil pleat / voile	2.5×	Fuller, more voluminous
Extra-full sheer	3×	Maximum fullness, very light fabric

Header Allowance Reference Table

Heading Style	Top Allowance
Rod pocket (standard)	8 cm
Pencil-pleat tape	10 cm
Eyelet / grommet	5 cm
Pinch-pleat hooks	12 cm

Linear Meters by Rod Width (2× fullness, 140 cm roll, rod-pocket heading)

Rod Width	Fabric Width	Panels	200 cm drop	230 cm drop	250 cm drop
90 cm	200 cm	2 panels	4.6 m	5.2 m	5.6 m
120 cm	260 cm	2 panels	4.6 m	5.2 m	5.6 m
150 cm	320 cm	3 panels	6.8 m	7.8 m	8.5 m
180 cm	380 cm	3 panels	6.8 m	7.8 m	8.5 m
200 cm	420 cm	3 panels	6.8 m	7.8 m	8.5 m
240 cm	500 cm	4 panels	9.1 m	10.4 m	11.3 m
280 cm	580 cm	5 panels	11.4 m	13.0 m	14.2 m
300 cm	620 cm	5 panels	11.4 m	13.0 m	14.2 m

Fabric length = drop + 8 cm header + 20 cm hem. Always round panels UP.

Worked Examples

Case 1 — Standard living room (150 × 250 cm, 2× fullness, rod pocket)
Fabric width = 150 × 2 + 20 = 320 cm. Fabric length = 250 + 8 + 20 = 278 cm.
From a 140 cm roll: ⌈320 ÷ 140⌉ = 3 panels × 278 cm = 8.34 m → buy 8.5 m.

Case 2 — Narrow bedroom with sheer voile (90 cm wide, 200 cm drop, 2.5× fullness, pencil pleat)
Fabric width = 90 × 2.5 + 20 = 245 cm. Fabric length = 200 + 10 + 20 = 230 cm.
From a 140 cm roll: ⌈245 ÷ 140⌉ = 2 panels × 230 cm = 4.6 m → buy 4.6 m.

Case 3 — Wide picture window with patterned fabric (220 cm wide, 270 cm drop, 2× fullness, 30 cm pattern repeat)
Fabric width = 220 × 2 + 20 = 460 cm. Fabric length = 270 + 8 + 20 = 298 cm.
From a 140 cm roll: ⌈460 ÷ 140⌉ = 4 panels. Add one pattern repeat per panel: 4 × 30 = 120 cm extra length.
Linear meters = 4 × (298 + 30) = 4 × 328 = 13.12 m → buy 13.5 m (patterned).

Common Mistakes

1. Measuring the glass pane instead of the rod — the rod is almost always 30–60 cm wider than the glass; using glass width leaves you badly short of fabric.
2. Forgetting the fullness multiplier — fabric bought equal to window width produces flat, skimpy curtains. 2× is the universally recommended minimum for a gathered look.
3. Confusing roll width with curtain width — the 140 cm roll width is used as the curtain LENGTH (drop direction). The curtain WIDTH is calculated from your fullness formula, and you cut multiple panels from the roll.
4. Ignoring pattern repeat — patterned fabrics need one extra full repeat per panel (25–64 cm typical) so motifs align between panels when sewn together.
5. Not pre-washing natural fabrics — cotton shrinks 3–5%, linen up to 8% on first wash. Pre-wash before cutting or add that margin to the length calculation.
6. Rounding down — always round fabric quantities UP to the nearest panel or half-meter. Fabric stores cut to set increments and running short mid-project means a new dye lot that may not match.

Living room: 150 cm wide rod × 250 cm drop, 2× fullness

Fabric width: 150 × 2 + 20 = 320 cm needed.

Fabric length: 250 + 8 (rod pocket) + 20 = 278 cm needed.

From a 140 cm roll: ⌈320 ÷ 140⌉ = 3 panels × 278 cm = 834 cm = 8.4 m to buy.

Buy 8.4 linear meters of 140 cm wide fabric (3 panels of 278 cm each)

Frequently asked questions

How much fabric do I need for a 150 cm wide window?

For a 150 cm rod with 2× fullness and 250 cm drop: Fabric width = 150 × 2 + 20 = 320 cm. From a 140 cm roll: 3 panels needed. Fabric length = 250 + 8 (rod pocket) + 20 = 278 cm. Total: 3 × 278 ÷ 100 = 8.34 linear meters. Buy 8.5 m to have a small safety margin.

Why multiply window width by a fullness factor?

A curtain panel equal in width to the window would lie completely flat against the wall with no folds — it would look like a bedsheet. The fullness multiplier creates the extra fabric that forms gathers, pleats, or soft folds. 2× is the professional standard: half the fabric is 'used up' in gathers and the other half creates the visual fullness.

Where exactly do I measure window width?

Measure the curtain rod or track end to end — NOT the window glass. Rods are typically installed 15–20 cm wider than the window frame on each side so that when the curtains are open they don't cover the glass and block daylight. If you haven't installed the rod yet, add 15–20 cm to each side of the window frame as a planning estimate.

How do I measure drop (curtain length) correctly?

Measure from the bottom of the rod (or from the bottom of the clip/ring if using rings) down to your desired finish point — floor level, 1–2 cm above floor, window sill, or 10–15 cm below the sill. Do NOT measure from the window frame. Rods are usually hung 10–15 cm above the frame, and that 'high hang' technique visually makes windows look taller.

What does the +20 cm at the bottom cover?

It accounts for a double-fold bottom hem: the fabric is folded up 10 cm and folded again another 10 cm, creating a double hem 10 cm deep. This professional finish hides the raw edge, adds weight to help the curtain hang straight, and gives a crisp, clean bottom line. If you prefer a single 5 cm hem, subtract 10 cm from this allowance.

How do I convert fabric width to linear meters to buy?

Fabric is sold by the linear meter from a roll (bolt) of fixed width — usually 140 cm. Divide the fabric width you need (in cm) by the roll width (140 cm) and round UP to the nearest whole number: that's the number of panels. Then multiply panels × fabric length (in cm) ÷ 100 to get linear meters. The calculator does this automatically for 140 cm rolls.

Does patterned fabric need extra yardage?

Yes. For patterned fabric, add one full pattern repeat length per panel. Common repeats range from 25 cm (small prints) to 64 cm (large medallion or floral motifs). For example, if you need 4 panels and the repeat is 30 cm, add 4 × 30 = 120 cm to your total fabric length before calculating linear meters. Always ask the retailer for the exact repeat measurement before purchasing.

Should I calculate lining fabric separately?

Yes. Lining is calculated independently. A standard lining typically uses 1.5× the rod width (less fullness than face fabric) plus the same drop length and hem allowance. For a 150 cm rod with 250 cm drop: lining width = 150 × 1.5 + 20 = 245 cm; lining length = 250 + 5 + 15 = 270 cm. Blackout lining usually costs more per meter than standard cotton lining.

Does fabric type (cotton vs. sheer vs. blackout) change the formula?

The formula stays the same, but the recommended fullness multiplier changes. Heavy blackout fabric: 1.8×–2× (the weight creates natural fall with less fullness). Medium cotton/linen blend: 2×. Sheer voile: 2.5×–3× (you need more fabric because sheers are translucent and sparse fullness shows immediately). Also, heavy fabrics may need a slightly wider side hem to carry the weight — the 10 cm side seam still applies.

Can I use this calculator for tab-top or eyelet curtains?

Yes. For eyelet (grommet) or tab-top styles, choose 1.5× fullness and 'Eyelet / grommet' as the heading style (5 cm allowance). These styles have less gather by design — the fixed spacing of eyelets or tabs doesn't allow the same fabric compression as gathered headings. The rest of the formula is identical.

Sources & references

Methodology & trust

Editorial

Calculadora de construcción revisada por el equipo editorial de Hacé Cuentas, contrastada con Cotswold Sewing School — Calculating Fabric for Curtains (2022), según nuestra política editorial y metodología.

Updates

Última revisión: June 20, 2026. Los parámetros se verifican periódicamente con las fuentes citadas.

Privacy

Calculations run 100% in your browser. We do not store or transmit your data.

Limitations

Indicative results. For critical decisions, consult a professional.

📌 How to cite this calculator

Rodríguez, M. (2026). Curtain Fabric Calculator — How Much Fabric Do You Need? (+ Reference Charts). Hacé Cuentas. https://hacecuentas.com/curtain-fabric-window-calculator

Contenido bajo licencia CC-BY 4.0 — reutilizable citando la fuente con enlace a Hacé Cuentas.

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