Fabric Calculator

Background.

A fabric calculator turns a set of cut pieces into yardage, and the reason it is not simple division is that pieces do not tile a bolt. Fabric arrives in one fixed width and any length you like, so the layout problem is one-dimensional packing: as many whole pieces as will fit across the usable width, then as many rows down the length as you need. Whatever strip is left over across the width is waste on every single row, and that strip is where most fabric budgets quietly go.

The worked example on this page makes the effect concrete. Twelve 18-inch napkins from 44-inch quilting cotton sounds like a straightforward area sum — 12 × 18 × 18 is 3,888 square inches, and a yard of 44-inch fabric is 1,584 square inches, so about 2.5 yards. The real answer is 3.3 yards. Take one inch off for selvage and 43 inches of usable width fits two 18-inch pieces with 7 inches wasted, so the twelve napkins need six rows of 18 inches, which is 108 inches of cloth, and after a 10 percent allowance that is 3.3 yards. Only 74 percent of the fabric you buy ends up in a napkin. Move the same project to 60-inch fabric and three pieces fit across, four rows do the job, and the answer drops to 2.2 yards — a third less cloth for identical napkins.

The page runs the question in both directions. Ask how many yards you need for a given number of pieces, or ask how many pieces come out of the yardage already in your cupboard, and the second is a genuine inverse rather than a restatement: it tells you whether you are short and by how many pieces. One deliberate asymmetry between the two: when you are buying, the shrinkage and cutting allowance is added on top of the cloth the layout needs, and when you are cutting from stock it is reserved out of the cloth you have. Adding it in the second direction would invite you to cut into fabric you have already set aside for shrinkage.

Three limits belong beside the answer rather than behind an accordion. Grain is fixed: the piece width runs across the bolt and the piece length runs down it, and rotating a piece ninety degrees changes the result — an option you do not have on a directional print or a piece that must hang on grain. Nominal width is not usable width: ASTM D3774, the standard test method for the width of textile fabric, measures a bolt including its selvages, so the 44 inches on the label includes edge you will trim, and the selvage loss here is a measurement to take from your own cloth rather than a constant anybody publishes. And the layout is a plain grid of rectangles — no nesting of irregular pattern pieces, no interlocking rotation, no bias, no cutting across a fold. A skilled cutter can beat this figure; a cutter working to grain on a directional print usually cannot.

The method itself, and the pattern-repeat rule that goes with it, is not invented here. It is the widths-and-cut-lengths approach set out in The Singer Company's 1960 trade manual How to Make Draperies, and when the piece width is set equal to the fabric width this calculator reproduces that manual's own published figures exactly — 9⅓ yards for four 84-inch lengths of 48-inch fabric, and 10⅔ yards once a 24-inch pattern repeat raises each cut to 96 inches.

What is fabric calculator?

Fabric yardage is the length of cloth, at a fixed sold width, that a cutting layout occupies. Three quantities decide it. The first is the usable width — the bolt width less whatever selvage you trim — because that is what limits how many pieces sit side by side. The second is the number of whole pieces that fit across that usable width, always rounded down, since a partial piece is not a piece. The third is the number of rows of pieces you need down the length, which is the piece count divided by the pieces across and rounded up, because you buy the whole row whether you use all of it or not.

Multiply the rows by the length each piece needs and you have the cutting length in inches; divide by 36 for yards. Where the fabric carries a vertical pattern repeat, each piece's length is first raised up to the next whole repeat so that the motifs land in the same place on every piece — a step that can add a substantial amount on long pieces with a large repeat.

The inverse question is the same layout read backwards. Given the yardage you have, how many rows fit — rounded down this time — and therefore how many pieces? That direction is what tells you whether the remnant in your cupboard is enough before you cut into it, and by how many pieces you fall short if it is not.

How to use this calculator.

1. 01Choose the direction: yards for a set of pieces, or pieces from the yardage you already own.
2. 02Enter the fabric width printed on the bolt — 44–45 in for quilting cotton, 54–60 in for apparel and drapery goods, 108 in for quilt backing.
3. 03Measure your selvage and enter the loss. ASTM D3774 measures bolt width including selvages, so the printed width overstates what you can cut from.
4. 04Enter the piece width — the measurement that runs across the bolt — and the piece length, which runs down it. Include seam allowance: enter the size you will cut, not the finished size.
5. 05Enter how many pieces you need. In the cutting-from-stock direction this becomes the target the result is checked against.
6. 06Enter the vertical pattern repeat, or 0 for a plain fabric. Repeats on long pieces are where projects overrun.
7. 07Set the shrinkage and cutting allowance. Pre-wash a sample, measure the change yourself, and use that — the 10 percent default is a starting point, not a figure for your cloth.
8. 08Read the yardage, then read the efficiency figure below it. If it is well under 80 percent, look at the leftover strip across the width: a different bolt width or a slightly narrower piece often removes a whole row.
9. 09Round the yardage up to whatever increment your shop cuts to, buy it, wash it, measure it again, and only then cut.

The formula.

Start with the usable width: the bolt width less the selvage you trim. Divide it by the piece width and round DOWN — that is the number of whole pieces that sit side by side across the fabric, and rounding down is not a simplification but the physical fact that two thirds of a napkin is not a napkin. On 43 inches of usable width an 18-inch piece fits twice, leaving a 7-inch strip that is wasted on every row.

Next, the cut length of one piece. If the fabric has no vertical repeat this is just the piece length. If it has a repeat, the length is raised UP to the next whole multiple of the repeat so that every piece starts at the same point in the pattern. That step is always a ceiling: a cut that lands short of the next repeat cannot be matched, and unlike buying too much fabric the mistake cannot be undone.

Then the rows. Buying, it is the piece count divided by the pieces across, rounded UP, because a row is bought whole. Multiply rows by cut length for the total cutting length, divide by 36 for yards, and apply your allowance. Cutting from stock, the direction reverses: the yardage on hand is converted to inches, the allowance is reserved out of it by dividing rather than added by multiplying, and the result is divided by the cut length and rounded DOWN — you cannot cut a row you do not have.

Working the published example: 44 in bolt less 1 in selvage is 43 in usable; ⌊43 ÷ 18⌋ = 2 pieces across; no repeat, so the cut length stays 18 in; ⌈12 ÷ 2⌉ = 6 rows; 6 × 18 = 108 in of cloth; 108 ÷ 36 = 3 yd, and × 1.10 for the allowance gives 3.3 yd, which is 3.01752 m at the exact factor 1 yd = 0.9144 m. Efficiency is the piece area over the fabric area bought: 12 × 18 × 18 = 3,888 sq in of napkins against 3.3 × 36 × 44 = 5,227.2 sq in of cloth, or 74.3801652893 percent.

Rounding happens at exactly three places, and each one is a quantity that is physically integral: pieces across (down), rows (up when buying, down when cutting), and the cut length against a pattern repeat (up). Everything else is carried at full precision to the end. The yardage is deliberately NOT rounded up to a saleable increment, because shops differ on whether they cut to the quarter or the eighth of a yard, and rounding here would both hide the real requirement and make the efficiency figure wrong.

A worked example.

Frequently asked questions.

References& sources.

1. [1]The Singer Company, How to Make Draperies, Book No. 102 (1960) — Project Gutenberg ebook 63282. PRIMARY SOURCE for the widths-and-cut-lengths method this page generalises, for the pattern-repeat allowance ("if you select a fabric with a large one-way design, some allowance should be made for matching the design so all lengths will balance"), for the fabric-width list ("Some fabrics are only 36" wide … Others may run 40"—48"—even 54" or 60" in width; but the average is about 48" wide"), and for the grain rule ("Draperies must be cut on the true lengthwise and crosswise grain of the fabric"). Its published example — 4 widths of 48" fabric at 84", giving 9⅓ yd plain and 10⅔ yd with a 24" repeat — is reproduced exactly by this page's general algorithm and asserted in its tests. Retrieved and every quotation confirmed 2026-07-30.
2. [2]ASTM International, ASTM D3774-18, Standard Test Method for Width of Textile Fabric — scope and Option A (full roll or bolt): "Unless otherwise specified, measurements shall include the selvages when present." Cited for the scope limit that a bolt's nominal width includes selvage, which is why usable width is a separate input here. PAYWALLED full standard; scope and title read on the publisher's own store page, 2026-07-30.
3. [3]AATCC, TM135, Test Method for Dimensional Changes of Fabrics after Home Laundering (current edition TM135-2025) — four wash temperatures, three agitation cycles and four drying procedures for measuring length and width change. Cited as the reason this page exposes shrinkage as a measured allowance rather than baking in a percentage. PAYWALLED full method; scope read on AATCC's own store listing, 2026-07-30.
4. [4]NIST, Physical Measurement Laboratory — Revised Unit Conversion Factors (U.S. survey foot deprecation), giving the international foot as exactly 0.3048 m; adopted 1 January 2023 and published in NIST Handbook 44 and NIST Special Publication 811, per Federal Register FR Doc 2020-21902. Source of the exact factor used for the metric output: 1 yd = 3 ft = 0.9144 m. Retrieved 2026-07-30.