WCAG 3.0 APCA Web Contrast Calculator
Real-time perceptual readability index (Lc) simulation matching text sizes and background/foreground luminance characteristics
Compute modern perceptual readability levels using the proposed WCAG 3.0 APCA specification. Better maps biological human eyesight response.
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How to use
- Adjust text and background colors via pickers or hex inputs.
- Instantly review the APCA contrast scale (Lc) and accessibility feedback.
- Tweak font sizes and weights in the live preview to test reading comfort.
FAQ
- What is the difference between WCAG 2.x and APCA?
- WCAG 2.x uses a simple math ratio independent of color positions, whereas APCA respects human eye response to light vs dark polarities, making it more accurate.
- What is a passing APCA score?
- An Lc of 75+ is recommended for standard body text. Lc 60+ is acceptable for larger/bold text, and Lc 45+ fits large headers or UI frames.
- What does it mean when the Lc value shows as negative?
- The sign in APCA depends on whether the background is lighter or darker than the text. A negative value means light text on a dark background, while a positive value means dark text on a light background. When judging the grade, just compare the absolute value and ignore the sign.