How much fabric do I need for curtains?

Calculate curtain fabric by combining the measured pole or track width with the maker’s fullness, hem allowance, roll width, and vertical repeat.

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ToolCurtain Size Calculator
Input
Output
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How it works

Rail width multiplied by fullness gives the required flat width, which is divided by usable fabric width and rounded up to complete vertical drops. Heading and hem allowance extend the finished drop, and patterned cloth rounds every drop up to the next whole repeat before the drop count is multiplied.

Formula
fabric length = whole fabric widths × repeat-adjusted cut length
flat fabric width = pole or track width × fullness ratio
  • Terrys describes fullness as a heading-specific preference rather than one fixed value, so the selected ratio is required.
  • Pattern repeat alone defaults to zero for plain cloth; finished drop, allowances, and usable roll width must come from the project.

Worked example

A 180cm pole with double fullness
A 180cm finished drop, 25cm total heading and hem allowance, 137cm fabric width
Input
											Track width cm: 180
Finished drop cm: 180
Fullness ratio: 2
Hem allowance cm: 25
Fabric roll width cm: 137
Output
												Fabric width needed cm: 360
Fabric drop needed cm: 205
Fullness ratio used: 2
Widths of fabric required: 3
Total fabric length needed m: 6.15

When to use this

Pencil-pleat orders measure a pole or track, eyelet orders measure finished drop from the pole, and patterned pairs cut every joined width to a complete repeat.

Edge cases

  • A 205 cm cut with a 30 cm vertical repeat becomes 210 cm for every drop, not just the first, so motifs can align across joined widths.
  • A requirement just over two roll widths rounds up to three complete drops and creates fabric joins rather than assuming a fractional-width purchase.
  • Eyelet and pencil-pleat headings use different suggested fullness ranges, so the ratio is read from the maker’s instructions instead of guessed from the heading label.

References