ContrastRatioAaVsAaa [fact] v1.0.0

WCAG 2.2 specifies two contrast tiers: AA (4.5:1 normal text, 3:1 large) is the legal compliance floor; AAA (7:1 normal, 4.5:1 large) is the recommended target for sustained reading and reflects the publishing-industry contrast standard.

WCAG 2.2 SC 1.4.3 requires luminance contrast ≥ 4.5:1 for normal text (Level AA) and SC 1.4.6 requires ≥ 7:1 (Level AAA) — AA is the legal compliance floor required by the EAA (EU 2025), DOJ Title II (US 2024), and most procurement frameworks; AAA approximates the contrast standard used by professional publishers for sustained reading and is recommended for long-form content.

Confidence

proven

Applies To

• normal-text contrast targets (body, label, caption)
• large-text contrast targets (heading, display)
• compliance gating in CI
• reading-app target choice (long-form prose should aim AAA)

Quantitative

• Aa Normal Text: 4.5:1
• Aa Large Text: 3:1
• Aaa Normal Text: 7:1
• Aaa Large Text: 4.5:1
• Large Text Definition: ≥ 18 pt regular OR ≥ 14 pt bold (≈ 24 px / 18.66 px on standard 96 dpi)
• Formula: (L1 + 0.05) / (L2 + 0.05) where L1 is the lighter relative luminance

Counter Conditions

• WCAG contrast formula is a sRGB-luminance approximation — the upcoming APCA model (used by WCAG 3 drafts) better predicts perceived contrast for thin / large text, especially light-on-dark.
• Decorative text and logotypes are exempt from both AA and AAA.
• Disabled controls are exempt (SC 1.4.3 explicit exception).

ContrastRatioAaVsAaa [fact] v1.0.0

WCAG 2.2 specifies two contrast tiers: AA (4.5:1 normal text, 3:1 large) is the legal compliance floor; AAA (7:1 normal, 4.5:1 large) is the recommended target for sustained reading and reflects the publishing-industry contrast standard.

WCAG 2.2 SC 1.4.3 requires luminance contrast ≥ 4.5:1 for normal text (Level AA) and SC 1.4.6 requires ≥ 7:1 (Level AAA) — AA is the legal compliance floor required by the EAA (EU 2025), DOJ Title II (US 2024), and most procurement frameworks; AAA approximates the contrast standard used by professional publishers for sustained reading and is recommended for long-form content.

Confidence

proven

Applies To

• normal-text contrast targets (body, label, caption)
• large-text contrast targets (heading, display)
• compliance gating in CI
• reading-app target choice (long-form prose should aim AAA)

Quantitative

• Aa Normal Text: 4.5:1
• Aa Large Text: 3:1
• Aaa Normal Text: 7:1
• Aaa Large Text: 4.5:1
• Large Text Definition: ≥ 18 pt regular OR ≥ 14 pt bold (≈ 24 px / 18.66 px on standard 96 dpi)
• Formula: (L1 + 0.05) / (L2 + 0.05) where L1 is the lighter relative luminance

Counter Conditions

• WCAG contrast formula is a sRGB-luminance approximation — the upcoming APCA model (used by WCAG 3 drafts) better predicts perceived contrast for thin / large text, especially light-on-dark.
• Decorative text and logotypes are exempt from both AA and AAA.
• Disabled controls are exempt (SC 1.4.3 explicit exception).

Sources

Confidence

proven

Source

• W3C WCAG 2.2 — SC 1.4.3 (AA) and SC 1.4.6 (AAA)
• EU European Accessibility Act (EAA) — June 2025 enforcement
• US DOJ Title II rule (2024) — WCAG 2.1 AA reference
• Lighthouse / axe-core contrast checks

Applies To

• normal-text contrast targets (body, label, caption)
• large-text contrast targets (heading, display)
• compliance gating in CI
• reading-app target choice (long-form prose should aim AAA)

Quantitative

• Aa Normal Text: 4.5:1
• Aa Large Text: 3:1
• Aaa Normal Text: 7:1
• Aaa Large Text: 4.5:1
• Large Text Definition: ≥ 18 pt regular OR ≥ 14 pt bold (≈ 24 px / 18.66 px on standard 96 dpi)
• Formula: (L1 + 0.05) / (L2 + 0.05) where L1 is the lighter relative luminance

Counter Conditions

• WCAG contrast formula is a sRGB-luminance approximation — the upcoming APCA model (used by WCAG 3 drafts) better predicts perceived contrast for thin / large text, especially light-on-dark.
• Decorative text and logotypes are exempt from both AA and AAA.
• Disabled controls are exempt (SC 1.4.3 explicit exception).