# Curtain fullness calculator

Curtain fullness is the ratio between the flat width of fabric in a finished curtain and the width of track it covers, so a 200 cm track at 2× fullness needs 400 cm of flat fabric — 200 cm in each curtain of a pair, before side hems and seams are taken out. Dividing that by the usable width of your fabric and rounding up to a whole width gives the width count; the calculator below does it in metric or imperial, and shows the fullness those whole widths really deliver, which is almost always more than the figure you asked for.

Source: https://fabricmeasure.com/calculators/curtain-fullness-calculator/
Last updated: 2026-08-20 (method v1)
Published by FabricMeasure.

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## The formula

```
span            = trackWidth + returns + overlap
requiredFlat    = span x fullness / panels
usable(W)       = W x fabricWidth - 2 x sideHem - (ceil(W) - 1) x 2 x seamAllowance
widthsPerPanel  = smallest whole W where usable(W) >= requiredFlat
fullnessYouGet  = panels x usable(widthsPerPanel) / span
```

Side hems apply to the two OUTER edges only; interior edges are seams. W is rounded UP,
never to nearest, so the fullness delivered is always at least the fullness requested.

## Fullness each heading style needs

| Heading | Minimum | Recommended |
| --- | --- | --- |
| Pencil pleat | 2x | 2.5x |
| Pinch pleat | 2x | 2.2x |
| Eyelet | 1.8x | 2x |
| Tab top | 1.5x | 1.8x |
| Wave | 2x | 2.2x |

Default side hem 8 cm per side, seam allowance 1.5 cm. Both are editable on the page.

## Worked example

200 cm track, a pair of pencil-pleat curtains at 2.5x fullness, 140 cm fabric.

| Step | Working | Result |
| --- | --- | --- |
| Span each curtain covers | (200 cm track + 0 cm returns + 0 cm overlap) ÷ 2 curtains | 100 cm |
| Flat fabric width needed, per curtain | 100 cm × 2.5 fullness | 250 cm |
| What one width of fabric gives | 140 cm roll − 16 cm side hems | 124 cm |
| Widths per curtain, rounded up | 2 × 140 cm − 16 cm side hems − 3 cm seams = 261 cm usable | 2 widths |
| Fullness you actually get | 2 × 261 cm ÷ 200 cm of span | 2.61× |
| Widths to cut in total | 2 × 2 curtains | 4 widths |

Answer: 2 widths per curtain, hanging at 2.61x fullness.

## Assumptions

- Fullness is a ratio of flat fabric width to track width; it says nothing about length.
- Half widths are a full-width cut split down its length, so they come in pairs.
- The fabric width entered is the full roll width, including selvedge.
- The fabric runs vertically. Railroading removes the width question entirely and is not modelled.

## Common questions

### What does 2x fullness actually mean?

It means the flat fabric in the finished curtain is twice the width of the track it covers. A 300 cm track with a pair of curtains at 2× carries 600 cm of flat fabric, 300 cm in each curtain, which then gathers back to 150 cm per side when the heading tape is drawn up.

### Why does the calculator give more fullness than I asked for?

Because widths are indivisible. A curtain that needs 1.4 widths has to be made from 2, and the surplus cloth has nowhere to go except into the gather. The result shows both figures for that reason: the fullness you set is a minimum, and the fullness you get is what will hang at the window.

### Can I use half widths to avoid buying a whole one?

Yes, and the calculator will use them when they suffice. A half width is a full-width cut split down its length and seamed to a full one, so halves come in pairs — with an odd number of curtains you pay for one you do not use. The seam also has to fall somewhere sensible in the curtain rather than down its centre.

### Does the fabric width in the calculator include the selvedge?

The figure you enter is treated as the full roll width, and the side hems are taken off it. If your fabric has a heavy selvedge that has to be cut away before making up, subtract it first and enter the usable width instead — on a narrow roll that difference can change the width count.

### How much fullness does each heading style need?

Eyelet and tab-top headings hang correctly from about 1.5–1.8×, pencil pleat and wave want 2× as a floor and look better at 2.2–2.5×, and pinch pleat is usually made at 2–2.2× because the pleats themselves consume the fabric. Below its minimum a gathered heading pleats unevenly.

## Related tools

- [Curtain fabric calculator](https://fabricmeasure.com/calculators/curtain-fabric-calculator/): Track width, drop, fullness and pattern repeat in; metres or yards to buy out, with every allowance adjustable.
- [Curtain heading tape calculator](https://fabricmeasure.com/calculators/curtain-heading-tape-calculator/): Tape, hooks and cord for a pair of curtains — and why hooks are not counted on the tape.
- [Curtain lining calculator](https://fabricmeasure.com/calculators/curtain-lining-calculator/): Lining on its own narrower roll, from the flat width your curtains already need.
- [Curtain heading types](https://fabricmeasure.com/charts/curtain-heading-types/): Five headings compared on fullness, allowance and what they cost in cloth.
- [Pattern repeat calculator](https://fabricmeasure.com/calculators/pattern-repeat-calculator/): The cut length a repeat forces, what is trimmed from every piece, and what matching the design costs.
- [Fabric width converter](https://fabricmeasure.com/conversions/fabric-width-converter/): Pattern written for one bolt width, fabric bought at another — work out the equivalent length.