Curtain Fabric Calculator

Count equal curtain widths, add drop allowances and a vertical repeat, then round the purchase length up.

How this calculation works

Flat width is rod width × fullness, plus two returns, plus the total center overlap. Fullness presets are 1.5, 2, 2.5, and 3. The suggested start is 2. A custom ratio is allowed.

For a pair, that flat width is split in half. Each half is divided by the usable fabric width and rounded up. The two counts are added, so a pair never lands on an odd width count.

Cut length is finished drop plus the top allowance you enter plus hem allowance. A vertical repeat rounds that length up. Total fabric is the width count times the cut length.

Worked example

80 in rod, 2× fullness, 54 in fabric, pair

Required flat width is 160 in, or 80 in per panel.

Each panel needs two 54 in widths, so the pair uses four widths. A single combined division would have suggested three, which cannot make two equal panels.

An 84 in drop with 8 in top and 8 in hem cuts at 100 in. Four widths use 400 in, which rounds up to 11.125 yd at 1/8 yd.

Assumptions and limitations

The top allowance is required. It is not silently treated as zero.
Hem allowance starts at 8 in as a suggestion. Heading construction can need a different number.
54 in is a suggested planning width, not the width of every drapery cloth.
Half-drop repeats, horizontal motif centering, asymmetrical placement, lining, and interlining are not calculated.
Fullness is not mapped to one named heading style.

Common questions

Why can’t a pair use three fabric widths?

The two panels are kept equal. Each panel is rounded up on its own, then the counts are added, so the total is even.

Which fullness should I use?

Published ranges commonly run from 1.5× to 3×, and some tapes use other ratios. Pick the preset that matches your heading, or type a custom ratio. Two times is only the suggested start.

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