Yarn Calc

How the estimates and substitution scores work

Yardage estimates start from a published chart. — The baseline ranges per project and yarn weight are transcribed from Lion Brand's published “How Much Yarn Do I Need?” chart (lionbrand.com), captured at build time; an automated test fails the site build if our copy ever drifts from the source. The chart has no lace-weight column, so the estimator says so instead of inventing one.
Size and gauge adjustments are editorial and always shown. — The chart is one-size; size multipliers (baby ×0.35 … adult 2X ×1.35 for sweaters) are this calculator's own constants, printed as their own step. If you enter a swatch gauge, the estimate scales in proportion to your stitches-per-inch vs the class standard, capped at ×0.7–×1.4 because past that the yarn is effectively a different weight class.
Substitution scores are computed from manufacturer specs, not vibes. — Weight class (same 25 pts, neighboring 10), ball-band knit gauge distance (up to 35), fiber family from the label's own content line (up to 25), yardage-per-gram density (up to 10 — two “worsted” yarns can differ by half in weight per yard), care compatibility (5, with a warning when a machine-wash original gets a hand-wash substitute). Candidates more than one weight class away are refused outright.
Discontinued means the maker says so. — A yarn is flagged discontinued only when its manufacturer's own page or catalog marks it that way; the flag's source is the same cited product page. Discontinued yarns are excluded from substitute lists and get their own “best substitutes” page instead.
Every number is cited and dated. — Yardage, grams, fiber, gauge and care come from the manufacturer's own product pages, fetched on the date printed in the dataset table. No number in this tool comes from memory or from third-party databases.
Honesty. — Estimates are planning figures for average patterns: when your pattern states yardage, the pattern wins. Substitution scores compare ball-band specs; they cannot see texture, halo, ply structure, or color — swatch before you commit.