What is WCAG AA contrast? The 4.5:1 ratio requirement explained for body text
Always meet WCAG AA for body text. It's not aspirational. It's the floor. Use a contrast checker during design, not as an afterthought. If your brand palette doesn't have accessible text-background pairings, create accessible variants for your digital products.
WCAG AA requires a minimum contrast ratio of 4.5:1 for normal text (under 18pt or 14pt bold) against its background. This is the legal accessibility standard in most jurisdictions (Section 508 in the US, EN 301 549 in the EU) and the minimum bar every website should clear.
By TechCompare · Updated
How this is calculated
A contrast ratio of 4.5:1 means the lighter color is 4.5 times as bright as the darker color, as measured by the WCAG relative luminance formula. Pure black (#000000) on pure white (#FFFFFF) has a ratio of 21:1, the maximum. A medium gray (#767676) on white has a ratio of exactly 4.5:1, barely passing. Designers often push body text lighter for aesthetic reasons ("it looks cleaner"), but anything below 4.5:1 is literally unreadable for users with low vision, color blindness, or in bright ambient light.
Verdict
The 4.5:1 ratio comes from the WCAG relative luminance formula (L1 + 0.05) / (L2 + 0.05), where L1 is the brighter and L2 the darker color, and it's the legal accessibility threshold in most jurisdictions (Section 508 in the US, EN 301 549 in the EU). Pure black on white reaches 21:1, while #767676 on white lands at exactly 4.54:1, the edge of passing, which is why designers who push body text lighter for aesthetics land on the wrong side of the ratio fast. The 4.5:1 number itself was chosen against roughly 20/40 vision and bright ambient light, which is why it catches users with low vision, color blindness, and outdoor-screen users in the same pass. Validate every text-background pair during design rather than retrofitting after the palette ships.