Interfacing Calculator

Because yardage measures LENGTH along a fixed-width bolt, not total area. A 60" nonwoven bolt covers three times the area per linear yard that a 20" woven bolt does, so the same total square-inch requirement converts to far fewer linear yards on the wider bolt. If you switch interfacing types mid-project, always re-check the bolt width before assuming your original yardage estimate still applies.

It depends on piece size and shape: small, curved pieces like collar points or cuffs waste more of the bolt proportionally (15-20% is typical) because their shapes tile poorly, while large, mostly-rectangular pieces like a jacket's full front facing waste less (around 10%) since more of the bolt gets used edge to edge. When in doubt, round up — running short mid-project on interfacing usually means an awkward dye-lot mismatch on a second trip.

Because most fabric retailers cut and sell interfacing in eighth-yard increments off the bolt, not in arbitrary decimal amounts. Exact Yards Needed shows the precise mathematical requirement, while Yards to Buy rounds that up to the nearest 1/8 yard so the number actually matches what you can order at checkout.

No — Total Area Needed and Total Area (sq ft) are both a function of piece count, average piece area, and waste factor only; the bolt's width doesn't change how much SURFACE AREA your pattern pieces require. Width only determines how that fixed area converts into linear yardage on a particular bolt, which is why switching to a narrower or wider interfacing changes Yards to Buy without touching the area figures at all.