Methodology

Last reviewed 2026-11-07 Maintainer: Hammad Iqbal

FiberCalc publishes free, in-browser knitting, crochet, sewing, and quilting calculators. This page explains how formulas are chosen, which primary sources we cite, how AI may assist copy (never unchecked math), and where we log corrections. Use it when you need provenance—not as a substitute for a pattern’s tested yardage chart.

How calculations work

Each calculator documents its formula on the tool page. Quilt tools use perimeter and panel arithmetic. Gauge tools use direct proportion from measured swatches. Unit tests in this repository cover the pure math modules.

Yarn density factors (site heuristic)

CYC publishes weight categories and typical gauges—not yards per square inch. FiberCalc yarn estimators therefore use an explicit site heuristic: yards ≈ width_in × length_in × density(weight, method) × (1 + waste%/100). Crochet multiplies the knit density by 1.28. Default waste is 10% for blankets/hats, 8% for scarves, and 15% for sweaters and amigurumi. These factors are planning averages, not a published standard—prefer a pattern’s tested yardage when available.

Worked check: 50 × 60 = 3,000 in² × 0.55 = 1,650 yd before waste; ×1.10 = 1,815 yd; ceil(1,815 ÷ 200) = 10 skeins. Crochet: 1,815 × 1.28 ≈ 2,323 yd.

Sources policy

I cite primary, publicly available standards when a tool depends on them:

• CYC Standard Yarn Weight System
• CYC Hooks & Needles
• CYC Body measurements / sizing
• CYC Woman size charts
• International Sleep Products Association (mattress industry context)

Craft “standard” blanket and quilt sizes are community conventions—patterns may differ. I only list a source when the page actually uses that data, and I re-check URLs when content changes.

What the tools leave out

• Dye-lot matching, shrinkage after washing, and highly textured stitch patterns that break averages.
• Longarm quilting fees, batting brand stretch, and directional fabric naps.
• Legal, medical, or professional design advice of any kind.

AI / automation disclosure

Drafts of explanatory copy may be written with AI assistance. Every formula, rate-style constant, and reference link is checked by Hammad Iqbal against the sources listed on each page before publication. Calculator math is implemented in TypeScript with automated tests—not generated at request time.

Correction log

• 2026-10-20 — Removed anonymous “FiberCalc Team” authorship; named Hammad Iqbal as sole maintainer. Fixed escaped newline characters that appeared as visible text between calculator fields. Pointed needle/hook sources at the live CYC Hooks & Needles chart.
• 2026-10-23 — SEO/AEO pass: GA module scripts, 308 trailing-slash Worker, expanded guides, tool→guide links, site-origin single setting for future custom domain.
• 2026-10-24 — Reconciled blanket yardage copy to the density table (1,815 yd / 10 skeins for a 50×60″ worsted knit throw at 10% waste); published density factors here; removed raw path text from guide FAQ JSON-LD.
• 2026-11-07 — Corrected 4-at-a-time HST formula to unfinished ÷ 0.64; aligned US 17 needle mapping to CYC 12.75 mm; labeled lace crochet gauge as DC; clarified sweater size presets and mattress sizes as heuristics/retail rounding; expanded thin hubs; refreshed citations and last-reviewed date.

Changelog

• v1.0 (2026-10-19) — Initial public release of yarn, gauge, sewing, quilting, and reference calculators.
• 2026-10-20 — Mobile SEO / trust pass: PNG Open Graph image, TrustBlock sources, mode-aware knitting gauge fields, compact cookie bar, Consent Mode v2 for GA4.
• 2026-10-23 — Guides expanded, new articles, llms.txt inventory, per-page OG images, audit guardrails.

Dates

“Last reviewed” and dateModified change only when formulas, sources, or substantive text change—not on routine redeploys. Canonical URLs always use the single PUBLIC_SITE_URL setting (documented in the repo as docs/CUSTOM-DOMAIN.md).