Helpful numbers.
Open assumptions.

Our tools use deterministic arithmetic, not AI-generated estimates. All diagrams are original schematics. The defaults are editable examples and are not universal making specifications.

Ready-made panels and packs

If balanced pairs are selected, we round the number in use up to an even number. Packs are then rounded up separately. Extra panels in a pack are labelled as spares; they do not count toward the displayed fullness of the panels in use.

The tool compares 1.5×, 2×, 2.5× and 3× as planning examples. Your heading tape, track or curtain supplier may specify a different ratio.

Plain face fabric, vertically joined

The fabric tool supports plain, non-directional fabric and equal curtains made from full-width drops, with an editable pencil-pleat heading allowance. It does not calculate lining, hardware, pattern matching, half-width joins, railroaded fabric or proprietary wave headings.

We choose the smallest whole number of drops per curtain that meets the requested flat width. All curtains in a pair have the same number of drops. Raw fabric length is the cut length multiplied by all drops for one window, then by the number of identical windows. Windows must use the same measurements, fabric and allowances. An optional extra percentage is added to the combined raw total, then that project total is rounded up once to the shop’s cutting increment. Rounding each window separately can give a different order quantity.

“Side hem allowance” is the total fabric consumed by every fold at one outer edge. “Join seam allowance” is the allowance on each joined raw edge, so each join consumes two of them.

A checkable worked example

For a 200 cm track at 2.5× fullness, two equal curtains need 250 cm of flat width each. A 140 cm roll, 1 cm selvage at each edge, 8 cm consumed per outer side hem and 1.5 cm at each joining edge gives 257 cm per curtain using two drops.

A 220 cm finished length plus 10 cm heading, 20 cm bottom hem and 5 cm trimming gives four 255 cm drops: 1,020 cm raw fabric. Add 5% to get 1,071 cm. A 50 cm purchase increment rounds the estimate to 1,100 cm (11 m).

Identical windows and optional cost

For three copies of the 11 m worked example, the combined raw fabric is 30.6 m. Adding 5% gives 32.13 m; a 0.5 m shop increment rounds the combined order to 32.5 m, rather than three separately rounded 11 m orders. Drop counts and order length are project totals; finished curtain widths and fullness remain per window.

You can enter an optional fabric price per metre or yard and choose a currency label. We multiply the rounded purchase length in that price unit by your unit price. No exchange rate is used. The estimate covers face fabric only, excluding tax, shipping, lining, hardware and labour. Example prices are fictional.

Rounding and limits

Calculations use centimetres internally, retain unrounded values, and round only panel counts, full-width drops and purchase increments upward. Displayed numbers are shortened for readability. The source includes technical bounds for extreme inputs; these are not making recommendations.

References and review status

The explanations draw on Sew Helpful’s curtain fabric method and the manufacturer references listed in each guide. These sources do not endorse this tool. Automated arithmetic checks have been written; independent workroom review and a physical sewing trial remain outstanding.

For a special fabric or heading, ask your fabric supplier or maker to check the plan before buying or cutting.