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.

Your track and your fabric

Units

MetricImperial

Track or pole width

cm

What the curtains hang from, finials excluded

Fabric width

cm

The roll width, as sold

Curtains

SingleA pair

Heading stylePencil pleatPinch pleatEyeletTab topWaveNeeds at least 2× to pleat properly

Fullness you want1.5× — flat, modern1.8× — light gather2× — standard2.2× — generous2.5× — full3× — very full

Split widths

Whole onlyAllow halves

A half width is a full-width cut split down its length

Hems, seams and fittings

Side hem, per side

cm

Charged to the two outer edges only

Seam allowance

cm

One side of a join between widths

Returns

cm

Twice the bracket projection, on a track

Centre overlap

cm

0 if the curtains simply meet

Fabric widths per curtain

2 widths

Hung on this track they gather to 2.61× fullness.

Flat fabric needed per curtain

250 cm100 cm of span × 2.5

What those widths give you

261 cmafter side hems and seams

Fullness you actually get

2.61×you asked for 2.5×

Widths to cut in total

4 widthsboth curtains, 280 cm of cloth across each

What the other width counts would give

Calculated on the measurements above, for this heading and fabric.

Widths per curtain	Usable flat width	Fullness
1	124 cm	1.24×
2 — chosen	261 cm	2.61×
3	398 cm	3.98×

How we got this

1. Span each curtain covers — 100 cm(200 cm track + 0 cm returns + 0 cm overlap) ÷ 2 curtains
2. Flat fabric width needed, per curtain — 250 cm100 cm × 2.5 fullness
3. What one width of fabric gives — 124 cm140 cm roll − 16 cm side hems
4. Widths per curtain, rounded up — 2 widths2 × 140 cm − 16 cm side hems − 3 cm seams = 261 cm usable
5. Fullness you actually get — 2.61×2 × 261 cm ÷ 200 cm of span
6. Widths to cut in total — 4 widths2 × 2 curtains

ResetReport a wrong result

Widths per curtain2 at 2.61×

Fullness, in one sentence

Fullness is a ratio, and only a ratio: the flat width of cloth in a finished curtain divided by the span of track that curtain covers. Nothing about it is a length, which is why the same number describes a bedroom window and a bay. At 2× a curtain contains twice as much cloth across as the space it hangs in; at 3× it contains three times as much, and the heading tape pulls the surplus into deeper folds.

That ratio is the first decision in any curtain job, because everything downstream depends on it. Fullness sets the width count; the width count sets how many cuts come off the roll; the cuts set the bill. A tenth of a point either way is invisible at the window and can be the difference between four cuts and six.

Why the answer is always a whole number of widths

A shop sells cloth by the length off a roll of fixed width. You can buy any length you like and no width other than the one the roll is. So when the arithmetic says a curtain needs 1.4 widths the honest answer is 2, and the surplus does not vanish — it becomes extra gather.

Two allowances complicate the count. The outer edges of every curtain take a side hem, which is fabric turned back on itself and lost from the flat width. Interior edges are not hems at all: where two widths are joined they cost a seam allowance each side and nothing more. Charging a side hem to every width — the intuitive reading — over-orders by roughly one hem per join, and it is the most common arithmetic slip in this part of the job.

The consequence is that usable width grows in uneven jumps. On a 140 cm roll with 8 cm side hems the first width yields 124 cm; the second adds 137 cm; every width after that adds the same 137 cm. The table the calculator prints beside its answer shows those jumps for your own measurements, which is the quickest way to see whether you are just over a threshold or comfortably inside one.

A worked example

A 200 cm track, a pair of pencil-pleat curtains at 2.5× fullness, in a 140 cm fabric. These are the calculator's own starting values, and the table below is generated by the function that produces the answer above it.

The requested 2.5× needs 250 cm of flat cloth per curtain. One width gives 124 cm, which is short; two give 261 cm, which clears it — so the answer is 2 widths and the curtains hang at 2.61× rather than 2.5×. That surplus is not an error to be corrected. It is the price of buying cloth in whole widths, and on this window it is small.

What different track widths need

Because usable width climbs in steps, the relationship between track width and cost is a staircase rather than a slope. Every row below is a pair of pencil-pleat curtains at 2.5× in 140 cm fabric, calculated the same way as the answer above.

Read down the last column and the staircase is obvious: some track widths land just inside a threshold and gather far more than was asked for, others land just outside one. If your window falls badly, the lever to pull is the fullness rather than the measurements — dropping a quarter of a point can remove a width per curtain, provided the result stays above what the heading needs.

What each heading style needs

What each style actually is is defined in the glossary; this section is about the fullness each one needs before it behaves.

Heading styles differ in how much cloth they consume to form a pleat, so each has a floor below which it stops behaving. These are the figures this site uses, and they are the middle of the range UK workrooms quote rather than a standard anyone published.

Pulled below its minimum a gathered heading does not simply look sparse — it fails to pleat. The tape gathers unevenly, the folds flatten out between hooks, and the curtain hangs in slabs rather than waves. Eyelet and tab-top headings are the exception because their folds are formed by the fittings rather than by the tape, which is why they work at ratios that would look starved on a pencil pleat.

Weight matters as much as ratio. A heavy interlined velvet holds a fold at 2× that a fine voile would lose entirely; sheer fabrics are routinely made at 2.5–3× for exactly that reason. The calculator cannot see your cloth, so treat the minimum as a floor rather than a target.

How to measure for this

1. Measure the track, not the window. Measure the full length of the pole or track, excluding finials. This is the span the curtains have to cover when closed.
2. Add returns and overlap if you have them. A track on brackets returns to the wall at each end, and a pair usually overlaps at the centre. Both are gathered fabric, so both belong in the span.
3. Take the roll width from the label. Furnishing fabric is commonly 137 or 140 cm. If a heavy selvedge has to be cut off before making up, subtract it and enter the usable width.
4. Pick the heading and the fullness. The heading style sets the minimum fullness that will pleat properly. Choose the fullness you want above that minimum, not below it.
5. Read the width count and the fullness you get. The answer is a whole number of widths per curtain. Check the fullness those widths deliver, and open "How we got this" to see where every centimetre went.

What this calculator leaves out

Fullness is a question about width alone, so this tool deliberately says nothing about length. It does not ask for your drop, it does not know your pattern repeat, and it does not produce a quantity to buy — a width count multiplied by a cut length is what gives you metres, and that is the job of the curtain fabric calculator, which uses this same width solver internally. If your fabric has a design to match, the pattern repeat calculator handles the other half.

• Half widths come in pairs. A half is a full-width cut split down its length, so an odd number of them leaves one spare. The calculator says so when it happens.
• The seam position is your decision. The maths counts joins; it does not care where they fall. A join down the centre of a curtain is conspicuous, so workrooms place full widths at the leading edge and put the part width at the outside.
• Railroading changes the question. On a fabric wide enough to run sideways there are no vertical joins at all, and fullness stops being a width problem. The calculator assumes the cloth runs vertically.
• Fullness is not gather at the top only. The ratio describes the whole curtain, and a heading tape that is drawn up too tight for the fabric in it will not hang straight however the sum came out.

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

Track width, drop, fullness and pattern repeat in; metres or yards to buy out, with every allowance adjustable.

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

Lining on its own narrower roll, from the flat width your curtains already need.

Curtain heading types

Five headings compared on fullness, allowance and what they cost in cloth.

Pattern repeat calculator

The cut length a repeat forces, what is trimmed from every piece, and what matching the design costs.

Fabric width converter

Pattern written for one bolt width, fabric bought at another — work out the equivalent length.

Updated 20 August 2026 · Method v1 · Written and maintained by Wickeey · Tell me if a result looks wrong