Calculation Methodology

How to Read These Estimates

The site does not use one universal yardage formula. The home page gives a quick estimate for repeated rectangular pieces. Each dedicated calculator uses a separate set of rules for its project type.

• Imperial measurements are calculated in inches. Metric entries are converted to inches internally.
• Fabric totals are rounded up to the next quarter yard, then converted using 1 yard = 0.9144 meters.
• Inputs are limited to practical numeric ranges so an empty, negative, or extreme value does not break the page.
• Optional cost figures multiply the displayed yardage by one price per yard. They do not model different prices for lining, backing, or other materials.
• A cutting list is a planning model, not a printable sewing pattern or a guarantee that every shape will nest exactly as shown.

Quick Home Estimate

The home calculator treats the project as one or more identical rectangles. It adds the selected seam allowance to both sides of the length and width. If the finished rectangle is wider than the fabric, it assumes full fabric-width cuts will be joined side by side.

cutLength = projectLength + 2 * seamAllowance
cutWidth = projectWidth + 2 * seamAllowance
widthsNeeded = ceil(cutWidth / fabricWidth)
adjustedCutLength = repeatSelected ? roundUpToRepeat(cutLength) : cutLength
rawYards = widthsNeeded * adjustedCutLength * pieces / 36
total = roundUpToQuarter(rawYards * (1 + overagePercent / 100))

A repeat choice uses a fixed planning value of 6 inches for small, 12 inches for medium, or 24 inches for large. Each cut length is rounded up to a whole repeat. This quick method does not rotate or nest pieces. Use a dedicated calculator when the project has shaped pieces, several materials, or a detailed construction method.

Upholstery Calculator

The upholstery calculator starts with a built-in panel template for the selected furniture type. The template turns the entered width, depth, and height into approximate panels such as the inside back, seat deck, arms, cushion faces, and boxing. A 1 inch allowance is added at each panel edge in these templates.

The engine packs each panel type across the fabric width in simple rows. If a panel is too wide but fits after a 90 degree turn, it is rotated. If neither side fits, the estimate assumes that the panel is pieced from multiple fabric widths. This is a straightforward row calculation, not a pattern-aware nesting optimizer.

• Small, medium, and large repeat categories add 10%, 20%, and 35% to base panel yardage.
• If an exact vertical repeat is entered, the repeat allowance is estimated as 4% plus the repeat divided by 120, capped at 40%. It does not align each upholstery panel to a chosen motif.
• One-way nap adds 15% after the repeat allowance.
• The entered preshrink percentage is applied after repeat and nap.
• The skill setting adds 15% for beginner, 10% for DIY, or 5% for professional as a cutting-waste allowance. The label changes only this allowance and does not certify a user's skill.
• Welt fabric is estimated from the entered linear feet, strip width, and usable bolt width. Skirt fabric is estimated from perimeter, fullness, height, and fabric width.

For sofas, sectionals, loveseats, and chaises, an upright result may also show a railroaded comparison. That comparison applies a 12% reduction, or 18% for a sectional. It is a planning shortcut, not a second panel layout. The main panel calculation already rotates an oversized panel when needed to make it fit.

The displayed lower range is 15% below the fabric subtotal. The upper range is 15% above the subtotal and then includes selected welt and skirt amounts. Because the ends are not built on exactly the same basis, use the range only as context and use the itemized total for the on-screen selection.

Furniture construction varies widely. The templates do not know the actual number of cushions, arm shape, tufting, hidden surfaces, repair pieces, or where a workroom will place seams. The loveseat and sectional currently reuse the sofa panel structure at different overall dimensions, so confirm those projects from an actual tear-down or a workroom cut list before buying expensive fabric.

Sewing and Garment Calculator

The sewing calculator uses a built-in body-measurement table for sizes XS through XXL and adds 1, 3, 5, or 8 inches of ease for the selected fit. It then creates simplified rectangular bounds for the pattern pieces associated with the garment, including the selected seam and hem allowances.

Pieces are sorted by length and placed on simple shelves across the bolt. A piece that is wider than the bolt is counted across as many fabric widths as it needs. When an exact pattern repeat is entered, each piece length is rounded up to the next full repeat. One-way nap adds 15% to the packed running length. Main fabric is multiplied by quantity and rounded up to a quarter yard.

• Lining is estimated as 80% of the rounded main-fabric yardage.
• Interfacing is estimated from the rectangular area of generated collar, cuff, facing, waistband, and placket pieces.
• The displayed total adds main fabric, lining, and interfacing even though these are normally purchased as separate materials.
• If custom size is selected with only a bust entry, waist falls back to bust minus 10 inches and hip to bust plus 2 inches. A missing custom length uses the garment's built-in length.

These generated pieces are not a commercial pattern. They do not model darts, grain lines, plaid matching, facings unique to a pattern, fabric stretch, garment design details, or the exact cutting diagram supplied with a pattern. If you have a pattern envelope, its fabric table should take priority.

Curtain and Drape Calculator

The curtain calculator calculates cut length and cut width separately. Header style supplies a fixed top allowance from 4 to 10 inches. Bottom hem is entered by the user. An outside mount adds 4 inches to length, plus width for overlap and the entered returns.

cutLength = drop + headerAllowance + hemAllowance + outsideMountOverlap
cutLength = roundUpToRepeat(cutLength)
rodWidth = windowWidth + outsideMountWidthAndReturns
fullWidth = rodWidth * fullnessRatio
cutWidthPerPanel = fullWidth / panels + 2 * sideTurn
fabricWidthsPerPanel = ceil(cutWidthPerPanel / (fabricWidth - 1))
mainYards = cutLength * fabricWidthsPerPanel * panels * windows / 36

Fullness choices are 1.5, 2, 2.5, or 3 times the rod width. One inch is removed from the fabric width for selvedges. If a panel needs more than one usable width, the result assumes those widths will be seamed. Main fabric is then rounded up to a quarter yard.

• Lining uses the same fullness width, a cut length of the entered drop plus 4 inches, and no side-turn or pattern-repeat adjustment.
• Valance yardage uses the same fullness and the selected header and hem allowances.
• Tiebacks use a fixed 24 by 6 inch rectangle, two layers for each panel.
• The grand total combines main fabric, lining, valance, and tieback yardage.

The result does not account for a different lining width, horizontal pattern repeat, motif placement between joined widths, shrinkage, fabric defects, pleat placement, or workroom-specific heading construction. Measure the actual pole or track when possible, especially for an outside mount.

Quilting Calculator

The quilting calculator starts from a preset or custom target size. It subtracts selected borders, creates a grid of whole blocks, and then reports the finished size produced by that grid. With no sashing, the block count rounds up. With sashing, the block count uses the largest whole grid that fits. The reported finished dimensions can therefore be larger or smaller than the starting target.

Each square is cut at the finished block size plus seam allowance on both sides. The total block count is divided evenly among the selected colours, rounded up for each colour. Blocks are counted across the usable fabric width, which is the entered width minus 1 inch. Rows are multiplied by cut block size, the selected top-fabric overage is added, and each colour is rounded up to a quarter yard.

• Sashing and straight border strips are estimated from their total strip length and cut width, with 10% extra.
• Binding uses the finished perimeter plus 12 inches for joins, 2.5 inch straight-grain strips, and a minimum of half a yard.
• Backing adds 4 inches on every side and seams together as many usable fabric widths as required.
• Batting is shown 3 inches larger on every side, but batting is not added to the fabric-yardage total.
• The grand total combines top fabrics, sashing, borders, backing, and binding.

The top calculation assumes simple square blocks and an even colour split. It does not calculate the individual pieces inside a patchwork block, directional cutting, fussy cutting, bias binding, pieced backs, or a longarmer's preferred backing margin.

Cushion and Pillow Calculator

The cushion calculator supports box, bench, round, and bolster shapes. Box and bench cushions use one long wrap for the top, front boxing, bottom, and back boxing, plus two side-boxing strips. Seam allowance is added to every relevant edge, and a separate zipper allowance is used when a zipper is selected.

In the standard box layout, the main wrap length and both side strips are added as separate running lengths. If width orientation is selected, the main wrap is rotated only when its complete length fits across the bolt. A selected repeat rounds the main running length up before side strips are added. Yardage is rounded per cushion and then multiplied by quantity.

• A bench cushion uses the box method. When its width exceeds the usable bolt width, the estimate multiplies the box-cushion yardage by the number of joined panels.
• A round cushion uses two enclosing squares plus a circumference-based boxing strip.
• A bolster uses one circumference-based body rectangle plus two enclosing squares for the circular ends.
• Piping is reported as a separate linear cord requirement. It is not added to the main fabric total as bias-strip fabric.

The current cushion method does not nest multiple panels into unused space across the fabric width, even when the interface reports how many panels could fit. It also does not center motifs, match boxing to cushion faces, allow for foam compression, or calculate extra fabric for cutting piping strips. Treat the cutting diagram as an explanation of pieces, not a scale-ready pattern.

How We Check the Calculations

The five dedicated calculators have automated checks built around representative inputs. These checks cover default projects, option changes, rounding, input limits, add-ons, and cases where a piece is wider than the fabric. When a calculation changes, the related examples and page explanations should be checked at the same time.

A passing check means the software produced the expected result for that example. It does not prove that a generalized template matches every real sofa, garment, curtain, quilt, or cushion. That is why the assumptions and limits remain visible here.

Reference Point for Unit Conversion

The yard-to-meter conversion follows the conversion factors published in the NIST Guide to the SI. That reference supports the unit conversion only. It does not validate this site's project templates, allowances, packing methods, or yardage estimates.

Corrections and Final Checks

If you find a result that looks wrong, please send the calculator page, every input, the result you received, and what you expected through the contact page. A reproducible issue is checked against the current engine and its tests. If the code is wrong, the correction should include a test that covers the same case when practical. If the result follows the code but the assumption is too broad, we update the explanation or calculation as appropriate.

Before buying fabric, check bolt width, shrinkage, nap, repeat direction, motif placement, flaws, and whether all pieces must come from one dye lot. For a costly or irreversible project, compare this estimate with the actual pattern, measured tear-down, or workroom cut plan.