Methodology
How the tools on this site are built, how their results are checked, and how directory listings earn their place.
How the tools are built
Lucky Graphics keeps its tools small, inspectable, and based on published standards rather than guesswork. Two tools are live today, and each one shows its working on the page.
- Contrast checker: The contrast checker converts each colour channel to its linear value, combines the channels into a relative luminance with the WCAG 2.1 weights (0.2126 for red, 0.7152 for green, 0.0722 for blue), then divides the lighter luminance plus 0.05 by the darker luminance plus 0.05. Results are read against WCAG 2.1: at least 4.5 to 1 for normal text and 3 to 1 for large text at level AA, and 7 to 1 for normal text at level AAA.
- Px to rem converter: The px to rem converter divides the pixel value by the root font size, which defaults to 16px, the default in most browsers. You can change the root size when a project sets a different base, and results are shown to at most four decimal places.
- On-page working: Each tool page prints the standard it follows and a worked example by default, so you can repeat the calculation yourself instead of trusting a bare number.
How tools and listings are verified
Building a tool is only half the work. Before a tool or listing stays on the site, it goes through checks a visitor can repeat.
- Known-value testing: Tool output is compared against hand-worked examples, including the black on white maximum ratio and equal-colour minimum, before a tool is published and after any change to its code.
- Listing checks: Directory assets are checked for an accessible preview, a working route to the creator's page, clear license terms, usable file quality, and a realistic use case. The full criteria are published in our editorial policy.
- License honesty: A listing states the license as the creator publishes it. If the terms are unclear, the listing says so instead of guessing, and creators' own pages remain the final authority.
Background on why this site works this way is on the about page, and the guides in the learn section show the same standards applied to longer topics.
Standards we rely on
Accessibility judgements on this site follow the Web Content Accessibility Guidelines (WCAG) 2.1 published by the World Wide Web Consortium (W3C), including its relative luminance and contrast ratio definitions. Unit conversions follow the CSS specification approach, where rem units resolve against the root element's font size.
When a standard changes, the affected tool page and this methodology are reviewed together so the explanation never drifts away from the calculation actually running on the page.
Limits and corrections
A contrast ratio is a strong signal, not a complete accessibility audit. Font choice, size, spacing, and context still matter, and the tools here do not test whole pages or certify compliance. Directory information can also age: creators change prices, files, and license terms after a listing is published.
If you find a wrong result, a broken link, or outdated license information, tell us through the contact page with the page address and the value you expected. Verified errors are corrected under the same commitment described in the editorial policy.
Frequently asked questions
How does the contrast checker calculate its ratio?
It converts each colour to its relative luminance using the WCAG 2.1 formula, then divides the lighter luminance plus 0.05 by the darker luminance plus 0.05. The result is the ratio shown on the tool, checked against the WCAG 2.1 AA and AAA thresholds described on this page.
Why does the px to rem tool default to a 16px root size?
Most browsers use a 16px default root font size, so 16px equals 1rem unless a project changes it. The tool lets you enter a different root size when your project uses one, and the conversion is always pixels divided by that root size.
Does Lucky Graphics test every asset in the directory by hand?
Every listing is checked against the criteria on this page before it is published: a working preview, clear license terms, usable files, and a realistic use case. Listings that only repeat a creator's marketing copy without passing those checks are left out.
What should I do if a tool result or listing looks wrong?
Send the page address and what you expected to see through the contact page. Verified errors in tool output, links, pricing notes, or license information are corrected, and the correction approach in our editorial policy applies.