Curtain fabric calculator

To find how much curtain fabric you need, multiply the track width by the fullness to get the flat width each curtain must cover, divide that by the usable width of your fabric to get a whole number of fabric widths, then multiply that count by the cut length — the finished drop plus a heading allowance plus a hem allowance, rounded up to a whole number of pattern repeats. The calculator below does this for metric or imperial measurements and shows every step, so you can adjust any allowance to match how your curtains are being made.

Your window

Units

MetricImperial

Track or pole width

cm

The track, not the window — it usually extends past the glass

Finished drop

cm

From the hook or ring position to the hem

Fabric width

cm

The roll width, as sold

Pattern repeat

cm

0 for a plain fabric

Curtains

SingleA pair

Heading stylePencil pleatPinch pleatEyeletTab topWaveSuggests 2.5× fullness

Fullness1.5× — flat, modern1.8× — light gather2× — standard2.5× — full3× — very full

Your shop cuts toNearest 10 cmNearest half metreWhole metresNearest ⅛ yardNearest ¼ yardExact requirementMost UK and European shops cut roll goods to the nearest 10 cm.

Allowances and fittings

Heading allowance

cm

Fabric turned down at the top

Hem allowance

cm

A double 10 cm hem uses 20 cm

Side hem, per side

cm

Applies to the two outer edges only

Returns

cm

Twice the bracket projection, on a track

Centre overlap

cm

0 if the curtains simply meet

Shrinkage allowanceNone — dry clean3% — washable5% — untreated natural

Buy this much fabric

10.6 m

11⅝ yd · the calculation needs 10.56 m

Fabric to buy

10.6 mnearest 10 cm

Actually needed

10.56 m4 cm spare

Fabric widths

4 cuts of 256 cm2 per curtain

Fullness you get

2.61×you asked for 2×

Pattern repeats per cut

81 cm trimmed per cut

Lining (bought separately)

9.7 m4 cuts of 242.5 cm

You will get 2.61× fullness, not 2×

Fabric is sold in whole widths, so the extra has to go somewhere and it goes into the gather. This is not an error — the curtains will simply hang fuller than the minimum you asked for.

Half-drop repeats need a little more

If the motif steps down by half a repeat between adjacent widths rather than lining up straight across, add half a repeat per extra width. The calculator assumes a straight repeat.

How we got this

1. Flat fabric width needed, per curtain — 200 cm(200 cm track + 0 cm returns + 0 cm overlap) × 2 fullness ÷ 2 curtains
2. Fabric widths per curtain — 2 widths2 × 140 cm − 16 cm side hems − 3 cm seams = 261 cm usable
3. Fullness you actually get — 2.61×2 × 261 cm ÷ 200 cm of track
4. Cut length before pattern matching — 255 cm220 cm drop + 15 cm heading + 20 cm hem
5. Cut length rounded to whole pattern repeats — 256 cm⌈255 cm ÷ 32 cm⌉ = 8 repeats × 32 cm
6. Total cuts to buy — 4 cuts2 widths × 2 curtains
7. Fabric for the cuts — 1024 cm4 × 256 cm
8. Pattern placement allowance — 32 cmone extra repeat, so the first cut can start where you want in the pattern
9. Total fabric required — 1056 cmcuts + placement + shrinkage
10. Buy, rounded up (nearest 10 cm) — 1060 cm1056 cm rounded up to the next 0.1 m

ResetReport a wrong result

Buy10.6 m

How this calculator works

The quantity comes from two independent measurements that are multiplied at the end: how many widths of fabric each curtain needs across, and how long each of those widths has to be cut.

Across: the track width multiplied by the fullness gives the flat width each curtain must cover. Divide that by the usable width of your fabric — the roll width, less the two outer side hems, less two seam allowances at every join — and round up to a whole width. You cannot buy part of a width, which is why the fullness you get is nearly always more than the fullness you asked for.

Down: the finished drop plus a heading allowance plus a hem allowance gives the cut length. On a patterned fabric that length is then rounded up to a whole number of pattern repeats, because every drop has to begin at the same point in the design or the motifs will not line up across the joins. One extra repeat is added on top, so the first cut can be positioned where you want it rather than wherever the roll happens to start.

Multiply the two together, add any shrinkage allowance, and round up to whatever length your shop will cut. The rounding is always upward. Buying half a metre too much costs a few pounds; buying a little too little means going back for more from a dye lot that may have sold out, which cannot be fixed.

A worked example

A 200 cm track, a 220 cm drop, a pair of pencil-pleat curtains at 2× fullness, in a 140 cm fabric with a 32 cm pattern repeat. These are the calculator's own starting values, and the table below is generated by the same function that produces the answer above.

Two things in that table surprise people. The first is the fullness: 2× was requested, but two whole widths deliver 2.61×, because 1.6 widths is not something a shop can cut. The second is the repeat — the cut length missed seven repeats by 1 cm and had to take an eighth, and that 1 cm is trimmed off every one of the 4 cuts. Without the pattern, the same window needs 10.2 m.

Heading allowances used

Choosing a heading style seeds the heading and hem allowances. These are the middle of the range UK workrooms use — they are not a universal standard, and every one of them stays editable under Allowances and fittings.

How to measure

1. Measure the track, not the window. Measure the full width of the curtain track or pole, excluding any finials. A track normally extends 15–20 cm past the window on each side.
2. Measure the drop. Measure from the hook, ring or eyelet position down to where the hem should finish — sill, below sill, or floor.
3. Check the fabric width and repeat. Take the roll width and the vertical pattern repeat from the fabric label. Enter 0 for the repeat if the fabric is plain.
4. Choose the heading and fullness. The heading style sets the heading allowance and suggests a minimum fullness. Pencil pleat needs at least 2×; eyelet works from 1.8×.
5. Read the result and the workings. Check the quantity to buy, then open "How we got this" to see every allowance used, and adjust any of them to match how your curtains are being made.

What this assumes

Curtain making has no single standard, so two calculators can both be right and still disagree. These are the assumptions behind the figure above. Every one of them is an editable input, and the methodology page explains each in full.

• The drop is measured from the hook, ring or eyelet position, not from the top of the pole. The difference is usually 2–4 cm, which matters on a floor-length curtain.
• Side hems apply to the two outer edges only. Interior edges are joins, and cost a seam allowance each side rather than a hem.
• The pattern repeat is a straight repeat. A half-drop repeat, where the motif steps down between adjacent widths, needs an extra half repeat per additional width and is not modelled.
• The fabric width is nominal. A roll sold as 140 cm is often 137–140 cm once the selvedge is trimmed. Enter the usable width if you know it.
• The fabric runs vertically. Railroading a wide fabric sideways can avoid joins entirely and often halves the quantity, but is a different calculation.
• Lining is a separate purchase and is shown as its own figure, calculated from a 137 cm lining with no pattern to match.

Common questions

Do I measure the window or the curtain track?

Measure the track or pole, not the window. A track normally extends 15–20 cm past the window on each side so the curtains can stack clear of the glass, and measuring the window instead is the most common reason a calculation comes out short.

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

Because fabric is sold in whole widths. If two curtains need 200 cm of flat fabric each and one width gives 124 cm, you have to buy two widths — 261 cm — and the extra becomes fullness. The result shows both the fullness you asked for and the fullness you will actually get.

How does a pattern repeat change how much I need?

Every drop has to start at the same point in the pattern or the motifs will not line up across the joins, so each cut length is rounded up to a whole number of repeats. A 255 cm cut against a 32 cm repeat becomes 256 cm. One extra repeat is also added so the first cut can be placed where you want it in the design.

Where do I measure the drop from?

From the hook, ring or eyelet position down to where you want the hem to finish — not from the top of the pole. The difference is usually 2–4 cm, which is enough to matter on a floor-length curtain.

Does this include lining?

The main figure is face fabric only. Lining is a separate purchase calculated from a narrower roll with no pattern to match, and is shown as its own result underneath.

Related tools

Curtain fullness calculator

How many widths each curtain needs at the fullness you want — and what whole widths really gather to.

Roman blind fabric calculator

Fabric and lining for a flat blind — no fullness, but the repeat still decides the cut.

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.

Standard curtain sizes

Ready-made drops and widths, in both systems — and what each width really gathers to.

Pattern repeat calculator

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

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