Editorial Policy

Last updated: April 2026

FibreCalcs publishes free calculators and educational content for sewing, quilting, knitting, and crochet. Every calculator result depends on the accuracy of the underlying formula, and every piece of educational content shapes how people plan their projects. We take both responsibilities seriously. This page explains how we source, verify, and maintain everything on the site.

Formula sourcing

Every calculator on FibreCalcs implements a formula drawn from a published reference. We do not invent mathematics or create novel calculation methods. The standard formulas used by professional curtain makers, quilters, and knitters are well-established, and our job is to implement them correctly and present them clearly.

Sources include the following types of references.

• Textile industry handbooks and pattern-making references.
• Published quilting guides from recognised authors and educators.
• Yarn industry standards from organisations such as the Craft Yarn Council.
• Professional curtain-making and upholstery training materials.
• Established craft community resources with verifiable provenance.

Each calculator page cites its specific source in a dedicated reference section. Where multiple sources agree on a formula, we cite the most accessible one. Where sources disagree, we note the discrepancy and explain which approach we use and why.

Formula verification

Citing a source is not enough. Every formula goes through a verification process before it appears on the site. This process has four steps.

1. The formula is implemented in code and tested against known input and output values from the cited source.
2. At least two worked examples are run through the calculator, with every intermediate value and final result verified against hand calculations.
3. Automated tests are written to catch regressions — if a code change accidentally alters a formula, the tests fail and the change is blocked.
4. Source links are checked to confirm the referenced material is still accessible and the cited information is accurate.

This is not a one-off process. Formulas are re-verified periodically, and any reader-reported discrepancy triggers an immediate review.

Worked example validation

Worked examples are not written separately from the calculator and hoped to match. Every worked example on the site uses a specific set of inputs that are run through the actual calculator code. The intermediate values and final results shown in the prose are the values the calculator produces. If the calculator changes, the worked examples are updated to match.

Each worked example includes four parts: a real-world scenario that provides context, a step-by-step calculation showing the working, an interpretation explaining what the result means in practice, and a takeaway with actionable advice. This structure ensures the example teaches rather than simply demonstrates.

Source citation

Every calculator page includes two types of source information.

• A formula source field naming the specific reference (book, article, or standard) from which the calculation method is drawn.
• Source links providing direct URLs to supporting references, where available, so readers can verify the maths independently.

We never fabricate citations. If we cannot find a verifiable source for a particular calculation method, we state that clearly rather than inventing a reference.

Content freshness

Fabric and yarn specifications change over time. Quilting cotton widths, yarn put-ups, and industry conventions evolve. To keep content accurate, we track three dates on every page.

• Last updated— the date the content was last meaningfully revised. This is the date shown to readers and included in structured data for search engines.
• Content review date— an internal date tracking when the page was last reviewed for accuracy, even if no changes were made.
• Cost data expiry— for any calculator that references material costs, the date after which those costs should be re-verified (set at six months from last verification).

These dates are not cosmetic. When a review date approaches, the page is queued for re-verification. Stale pages are updated or flagged rather than left to quietly drift out of accuracy.

AI disclosure

FibreCalcs is built with the assistance of AI tools. This includes code generation, content drafting, testing, and design implementation. We are transparent about this because it matters for trust.

Here is what AI does and does not do on this site.

• AI assists with writing code, drafting educational content, and generating test suites.
• AI does not make editorial decisions about which formulas to use or how to present results.
• Every formula is human-verified against published textile industry sources before publication.
• Every worked example is validated by running the actual calculator code, not by asking an AI to produce plausible-looking numbers.
• Content is reviewed for AI-typical patterns (vague language, generic phrasing, unverified claims) using automated validators, and flagged content is rewritten.

The AI helps us build faster. The domain research, formula verification, and editorial standards are human-driven.

Error reporting

If you find an error in any calculator, worked example, or educational content, we want to know. Use the feedback form on any page to report the issue. Include the specific calculator, the inputs you used, and the result you believe is incorrect. Every report is reviewed, and confirmed errors are corrected as quickly as possible.

Calculator accuracy matters. A wrong result means someone buys too little fabric, runs out of yarn mid-project, or cuts a set of curtains two inches short. We would rather hear about errors than let them persist.

Independence

FibreCalcs is independently operated. We have no affiliate relationships with fabric shops, yarn suppliers, or pattern companies. Calculator results are not influenced by any commercial interest. When we mention a brand, product, or supplier in educational content, it is for context or example only — not because we receive compensation.

The site is free, carries no advertising, and requires no login. This is funded as a portfolio project, not a revenue stream, and that independence is reflected in the editorial decisions.