The question a yardage calculator cannot answer
Yardage calculators run forwards: you know the project, they tell you what to buy. This one runs backwards. You have a yard of something lovely, or a half-yard bundle, or the end of a bolt, and the question is what it will actually make. Every answer comes from two floor divisions — how many pieces fit across the usable width, how many rows fit down the length — and their product.
The floors matter more than they look. Forty-three inches of usable width divided by a 2.5 in cut is 17.2, and the 0.2 is not a fifth of a square, it is a half-inch strip of scrap running the whole length of the fabric. The same fabric divided by 5 in cuts gives 8.6 across, and now three inches of every row is wasted. That is why two cut sizes only two inches apart can differ by ten percentage points of waste, and why the reference table below is worth a glance before you commit to a size.
The calculator also compares both orientations. Turning a 5 × 7 in piece so its long side runs across the fabric changes the yield from 40 pieces to 42 on the same yard. That is a free gain when the print is non-directional and the piece is not load-bearing, and a mistake when it is neither.
Usable width, floors, and the waste denominator
Start with the usable width. Bolt width is measured selvage to selvage, but the selvage itself is woven more densely than the body of the cloth, often with pin holes from the tenter frame, and it will not press flat inside a seam. Cutters routinely lose between half an inch and an inch across the width. Measure your own — quilting cotton sold as 44 in frequently gives 42 to 43 in of clean fabric, and treating it as 44 is the single most common reason a cut list comes up one piece short.
Then the two divisions, both floored. floor((W − s) ÷ w) is the pieces across; floor(L ÷ l) is the rows. Multiply. There is no clever nesting here and that is deliberate: this is a guillotine layout, the way a rotary cutter and a long ruler actually work, where every cut runs the full width or the full length of the piece being subdivided. True irregular nesting can beat it, but not with straight rectangles.
Waste is measured against the whole purchased rectangle, W × L, not against the usable area. That is the honest denominator, because you paid for the selvages too. It means the reported waste can never fall below the share the selvages take: on 44 in goods with 1 in of selvage, that floor is 2.3% before a single cut is made. If you want waste measured only against what you could theoretically cut, subtract that floor.
The leftover figures tell you what shape the waste is in, which matters far more than its percentage. A 0.5 in strip beside the selvage is bin fodder. A 3.5 in strip is a binding, a sashing run, or a row of smaller pieces. Two layouts with identical waste percentages can be worth very different amounts depending on whether the offcuts are usable rectangles or slivers.
Worked example: 2.5 × 6.5 in rectangles from one yard
You have one yard of 44 in quilting cotton that cost $12 a yard, and you want 2.5 × 6.5 in rectangles for a brick-pattern quilt. You measure the selvages and lose 1 in across the width in total.
- Usable width. 44 − 1 = 43 in.
- Pieces across. 43 ÷ 2.5 = 17.2, so floor to 17 across.
- Rows down. 36 ÷ 6.5 = 5.54, so floor to 5 rows.
- Total. 17 × 5 = 85 rectangles.
- The other orientation. 43 ÷ 6.5 = 6.6 → 6 across; 36 ÷ 2.5 = 14.4 → 14 rows; 6 × 14 = 84. The first layout wins by one.
- Leftovers. Along the selvage: 43 − (17 × 2.5) = 43 − 42.5 = 0.5 in. At the end: 36 − (5 × 6.5) = 36 − 32.5 = 3.5 in.
- Waste. The pieces are 85 × 2.5 × 6.5 = 1,381.25 in²; the whole yard is 44 × 36 = 1,584 in². Waste = 1 − 1,381.25 ÷ 1,584 = 12.80%.
- Cost each. $12 ÷ 85 = $0.1412 per rectangle.
The 3.5 in end is the interesting leftover. It is too short for another row of 6.5 in rectangles, but it is 43 × 3.5 in of clean fabric — enough for seventeen more 2.5 in squares, or a run of 2.25 in binding strips. Whether you count it as waste depends entirely on whether you have a use for it.
What counts as a good yield
Under 10% waste is a well-chosen cut size on standard-width goods. Between 10% and 25% is normal and usually not worth chasing. Above 25% the cut size is fighting the fabric width, and the calculator says so.
The lever that moves waste most is the cut size, not the fabric. Look down the reference table: on the same yard, 2.5 in squares waste 6.1% while 10 in squares waste 24.2%, and both are perfectly sensible cuts. Large pieces waste more because the remainder after each floor division is a larger fraction of the piece — 43 ÷ 10 leaves 3 in unusable, and 3 in is a lot next to a 10 in square.
The second lever is buying a length that suits the piece. If your piece is 6.5 in long, a yard gives five rows and throws away 3.5 in; buying 39 in gives six rows and throws away nothing. That is a 20% gain in pieces for an 8.3% gain in fabric. Whenever you are buying rather than using stash, round the length up to a whole multiple of the piece length before you get to the cutting table.
Finally, check the orientation warning. If the calculator has rotated your pieces to gain a row, the piece length is now running on the crosswise grain. On a quilt block that is usually fine and is how strip piecing works anyway. On a garment facing, a waistband, or anything that must not stretch, it is not: crosswise grain has noticeably more give than lengthwise, and a directional print will run sideways. Untick rotation and accept the smaller yield.
Square cuts from one yard of 44 in fabric
| Square size | Across | Rows | Total squares | Waste |
|---|---|---|---|---|
| 2.5 in | 17 | 14 | 238 | 6.09% |
| 3.5 in | 12 | 10 | 120 | 7.20% |
| 4.5 in | 9 | 8 | 72 | 7.95% |
| 5 in | 8 | 7 | 56 | 11.62% |
| 6.5 in | 6 | 5 | 30 | 19.98% |
| 10 in | 4 | 3 | 12 | 24.24% |
Each row is floor(43 ÷ size) × floor(36 ÷ size), and the waste is 1 − total × size² ÷ 1,584. Change the fabric width or length in the calculator and the same table is rebuilt on your numbers.
What this layout does not account for
- Pattern repeat and matching. A large-scale or directional print forces pieces onto specific positions, which can cost far more than the nesting waste. Work the repeat out first with the pattern repeat calculator.
- Shrinkage. If you prewash after cutting, every piece shrinks. Cut oversize using the shrinkage calculator, or prewash the yardage first and re-measure the width — prewashed 44 in cotton often measures 42 in.
- Fabric flaws. Mills allow a small number of flagged flaws per bolt. On a long cut, plan to lose at least one piece to a printing skip or a slub.
- Irregular shapes. Triangles, curves and garment pattern pieces nest far better than their bounding rectangles suggest. This calculator will underestimate their yield, sometimes badly.
- Fold-and-cut error. Cutting through a doubled layer doubles a misaligned fold into a bowed piece. The yield is unchanged; the accuracy is not.
- Nap and one-way finishes. Velvet, corduroy and brushed fabrics must all run the same direction, which removes the rotation option even on a plain colour.
Buy the length that suits the piece
Fabric is sold by the length and the width is fixed, so the length is the only dimension you control. Whenever the row height divides the length badly, buying a little more gains a whole row. A 6.5 in piece into 36 in gives 5 rows with 3.5 in left; into 39 in it gives 6 rows with nothing left. You bought 8.3% more fabric and got 20% more pieces. Divide the length you are about to ask for by the piece length, and if the fraction is above about 0.5, round the purchase up.
How this fits with the rest of the cutting plan
Use this calculator when the fabric is fixed and the question is yield. Use the fabric yardage calculator when the project is fixed and the question is purchase. Most projects need both, in that order: work out what to buy, then check what the piece you actually bought will cut.
For quilts, the yield feeds directly into the layout. Once you know how many blocks a fabric gives, the quilt block count calculator fits them to a bed size with sashing and borders, the binding calculator handles the strips around the outside, and the backing yardage calculator deals with the seaming on the back, where the same floor-division problem appears in reverse.
The underlying problem — fitting identical rectangles onto a fixed-width roll — is the one-dimensional cutting-stock problem that paper mills, sign shops and vinyl cutters all solve. The HTV and vinyl roll calculator is the same arithmetic applied to a heat-transfer roll, and the reason both look alike is that both start from a width you cannot change and a length you can buy in whatever quantity you like.