Cut sizes, yardage and circle skirts
Fabric buying fails in one direction: too little, discovered mid-layout, in a dye lot that no longer exists. This page does the arithmetic that prevents it. Mode 1 turns finished panel dimensions into cut sizes with your seam and hem allowances, lays the panels across the fabric’s usable width, matches a pattern repeat when the fabric has one, and inflates for shrinkage, ending at a length to buy. Mode 2 does the circle-skirt geometry: waist radius from the circle fraction you choose, the full cutting radius, and the fabric the circle truly needs, with an honest warning when the circle is wider than the cloth.
Mode 1: panels and yardage
Mode 2: circle skirt
Disclaimer: This calculator gives estimates for general information only. It is not financial, medical or other professional advice. Yardage assumes a straightforward layout on straight grain; bias cuts, directional prints and pattern matching beyond the stated repeat can need more, and the fabric shop’s table is the final check.
What this calculator does
It does the two fabric calculations that decide a purchase. For rectangular work (curtains, panels, cushion covers, quilt backs and their kin) it builds the cut size from the finished size plus allowances, in the places allowances actually go: seam allowance on both width edges and the top, hem once at the bottom. It then lays panels across the usable width of the cloth (the width after selvedges, not the number printed on the bolt end), counts the rows the layout needs, stretches each row to a whole pattern repeat when matching matters, and adds shrinkage on top, reporting both the exact length and a buy figure rounded up to the quarter yard, which is how fabric is actually sold. For circle skirts it derives the waist radius from the chosen circle fraction, the single geometric fact the whole garment hangs from, and returns the cutting radius and the square of fabric the circle occupies, warning when the circle’s diameter exceeds the cloth’s usable width, because that changes the construction, not just the yardage.
How to use it
- Usable width is not bolt width. A 45 inch fabric yields about 44 usable after the selvedges, a 60 inch about 58-59. Enter the usable figure. One inch of optimism here is the difference between a layout that fits and a panel that must be pieced.
- Allowances are per the pattern’s construction. The defaults (half-inch seams, one-inch hem) suit home sewing norms; a pattern that specifies different allowances governs. Entering them wrong does not produce a wrong-looking answer, which is exactly the danger: it produces a neat, precise, short length of fabric.
- Repeat matching is a length cost, not a nicety. On a patterned fabric, rows must start at the same point of the motif or the panels visibly disagree; the mode rounds each row up to a whole repeat for that reason. On plains and textures, leave the repeat at zero and pay for no air.
- Shrinkage belongs in the wash, not the arithmetic. The shrinkage field exists for fabrics you cannot or will not pre-wash. For everything else, wash the fabric as the garment will be washed, then measure and cut; yardage bought for shrinking that never happens is yardage wasted in the other direction.
- Circle skirts: add the waistband seam in your head. The waist radius is derived from the waist circumference itself; a waistband or elastic casing consumes a seam’s worth at the top, which experienced makers take from the length. The cutting radius printed already includes your hem; cut the waist opening at the radius shown, and let the skirt hang before hemming, because the bias sections will drop.
How it is calculated
- Cut size: cut width = finished width + 2 x seam allowance. Cut length = finished length + seam allowance (top) + hem allowance (bottom).
- Layout: panels across = floor(usable width / cut width); a cut width above the usable width is reported as a layout problem, not silently stacked. Rows = ceiling(panels / panels across). Row length = cut length, rounded up to a whole number of pattern repeats when a repeat is given. Total length = rows x row length. With shrinkage s: length / (1 – s/100). Yards = inches / 36; the buy figure is the yardage rounded up to the next quarter yard.
- Circle skirt: waist radius r = waist / (2 x pi x f), where f is the circle fraction (1, 0.75, 0.5, 0.25). Cutting radius = r + finished length + hem allowance. The circle occupies a square of side 2 x cutting radius; fabric length needed is that side (cut from a double fold for a full circle), and the width check compares the same diameter with the usable width.
Worked examples
Two curtain panels. Finished 40 x 60 inches each, half-inch seams, a 2 inch hem, on 44 inches usable: cut size 41 x 62.50 inches. One panel fits across, so two rows: 125 inches, 3.47 yards. Add a pattern repeat of 8 inches and each row stretches to 64 inches: 128 inches, 3.56 yards, buy 3.75 yards. Skip pre-washing a cotton with 5% shrinkage instead, and the plain-fabric need becomes 131.58 inches, 3.65 yards, the same 3.75 on the ticket, arrived at by a different risk.
A full-circle skirt. Waist 28 inches, finished length 24, hem 1 inch: the waist radius is 4.46 inches, the cutting radius 29.46 inches, and the circle needs a square 58.91 inches across, 1.64 yards of length, and a fabric at least that wide or a seamed construction. On a 44 inch fabric the width warning fires, correctly: most full circles in fashion fabric are cut in panels for exactly this reason.
Reading your results
Read the cut size as the number to mark and cut by, and check it once against the pattern’s own cut list if one exists; disagreements are usually allowance conventions, and finding them before cutting is the entire value. Read the exact yardage beside the buy figure: a need of 3.51 yards buys 3.75, and the quarter yard of slack is your insurance against a miscut, priced honestly. Read any width warning as a change of plan (rotate the layout, piece the panel, or choose wider fabric), never as a rounding detail.
Limitations
- Layouts here are rectangular and on-grain. Bias cutting, one-way prints with a top and bottom, large motifs needing placement (not just repeat), and pieces that interlock (sleeves against bodies) all depart from rows-across arithmetic, usually upward. The estimate is a floor for simple work, not a ceiling for fancy work.
- Circle geometry assumes the standard construction. Panelled circles, gored skirts and circles with a yoke divide the geometry differently. Mode 2 gives the true circle; patterns that approximate it with gores need their own piece arithmetic, though the waist radius relation still governs the waist fit.
- Shrinkage varies within a stated fibre. Weave, finish and washing temperature move it. The field applies the percentage you enter uniformly to length; width shrinkage is not separately modelled, and a fabric that shrinks unevenly will tell you so in the wash, which is again why pre-washing beats arithmetic.
- Remnants and defects are real-world taxes. Bolt ends, flaws to cut around, and the shop’s minimum cut all sit outside the math. The quarter-yard round-up absorbs small ones; projects cut close to the bone deserve their own extra allowance entered through the panel count or a longer finished length.
Frequently asked questions
How much fabric do I need for my project?
Build the cut size first (finished size plus seam allowance on the seamed edges and hem at the bottom), divide the fabric’s usable width by the cut width for panels across, and multiply the rows that layout needs by the cut length, stretched to whole pattern repeats on patterned cloth. The worked example: two 40 x 60 panels on 44 inch fabric need 3.47 yards plain, 3.75 to buy once a repeat is matched. The calculator performs each step visibly so a suspicious figure can be traced to the step that produced it.
How do I calculate a circle skirt’s fabric?
From the waist: the radius of the waist opening is the waist divided by 2 pi for a full circle (and by 2 pi times the fraction for lesser circles), so a 28 inch waist opens at a 4.46 inch radius. Add the skirt length and hem to get the cutting radius (29.46 inches here), and the fabric must cover the circle’s diameter, 58.91 inches, in both directions, which is the number that decides between a seamless cut and panels. Mode 2 runs the whole chain and flags the width problem before the fabric is bought.
What is a pattern repeat and why does it cost fabric?
The repeat is the length over which a printed or woven pattern completes one full motif. Panels cut from different points of the motif will not match at the seams, so each row of the layout must begin at the same motif point, which wastes the partial repeat at each row’s end. On an 8 inch repeat the worked example’s rows grow from 63 to 64 inches; on a 24 inch repeat the same project grows by up to 23 inches a row, which is why large repeats carry a yardage warning on the pattern envelope itself.
Should I pre-wash fabric or add shrinkage allowance?
Pre-wash, whenever the fabric tolerates it: it converts an estimate into a fact, reveals colour bleeding and hand changes before cutting, and makes the shrinkage field unnecessary. The allowance route exists for dry-clean-only and structured fabrics, and for cases where the garment itself will never be washed differently. If you use it, measure the shrinkage of a washed sample square rather than trusting a generic percentage, and enter that: the calculator multiplies faithfully whatever it is given.
Related calculators
Method: cut sizes from finished dimensions with per-edge allowances as stated, rows-across layout against usable width with whole-repeat row stretching, shrinkage applied to length, and circle geometry from the waist-radius relation, exactly as defined on this page. Last reviewed: 13 October 2026.