Check a text and background pair against every WCAG 2 threshold at once, with a live sample in both sizes and the ratio as you adjust the colors.
Large text reads at a glance
Body copy is the harder case: it carries the detail, it is set smaller, and it is where a ratio that looked fine in a heading starts to cost people readability.
4.5:1 for body text at AA and 7:1 at AAA. Large text, meaning 24px regular or 18.66px bold and above, drops to 3:1 at AA and 4.5:1 at AAA. Interface parts and meaningful graphics need 3:1.
It means it clears a floor. The ratio is a formula over relative luminance, and it says nothing about typeface weight, size or the surrounding colors. Treat a pass as necessary rather than sufficient, and look at the sample above the numbers.
Both fields open an OKLCH picker, so you can nudge lightness on its own and watch the ratio move, which is usually the fastest route from a failing pair to a passing one that still looks like the brand.
It is the contrast model proposed for WCAG 3, and it matches how text actually reads far better than the ratio here does, particularly for light text on dark backgrounds. It is not yet what anyone is audited against, so the honest answer is to pass WCAG 2 and use APCA to settle arguments.