What it does
The APCA Contrast Calculator measures a text and background pair using an Lc lightness-contrast score. It combines a reference-text preview with font-size and weight tables, colour swapping, transparent text handling and shareable pair links.
Enter the text or icon colour on the left and the background on the right. CSS names, hex values and RGB forms are accepted. Their order matters: light text on a dark surface produces a negative Lc score, which indicates direction rather than an error.
Use the absolute score in the font table to compare suitable sizes and weights. The table’s sizes use CSS pixels, and the reference text is displayed at its stated size and weight. This connects a proposed colour pair to the type treatment it will accompany.
Transparent text is blended with the background before calculation or link sharing. Swapping it into the background also removes that transparency after blending. The site labels its contrast guidance preliminary and the APCA-W3 implementation beta; an Lc value is not a WCAG 2 ratio.
Strengths
- Foreground and background roles are explicit in the calculation.
- Font tables provide more context than a single contrast number.
Watch out for
- Shared links contain blended colours rather than the original text alpha.
- The guidance and reference tables are preliminary.
Best for
- Designers examining the relationship between text contrast and typography.
Sources
- APCA Contrast Calculator (Oct 28, 2026)
- GitHub - Myndex/apca-w3: The APCA version, to be licensed for use with guidelines: W3/AGWG. · GitHub (Oct 28, 2026)
- apca-w3/LICENSE.md at master · Myndex/apca-w3 · GitHub (Oct 28, 2026)