WCAG 2.1 Relative Luminance & AA / AAA Color Contrast Ratio Calculator

Verify WCAG 2.1 AA (4.5:1) and AAA (7.0:1) text accessibility contrast ratios.

WCAG 2.1 Contrast Ratio
7.46 : 1
Margin vs. WCAG AA Normal Text (4.5:1) 2.96 pts
Margin vs. WCAG AAA Normal Text (7.0:1) 0.46 pts
Margin vs. UI / Large Text (3.0:1) 4.46 pts
Inputs
L₁ (0–1)
Relative luminance of lighter color L₁ (0.00 pure black to 1.00 pure white).
L₂ (0–1)
Relative luminance of darker color L₂ (0.00 pure black to 1.00 pure white).
Results & Graph
WCAG 2.1 Contrast Ratio
7.46 : 1
Margin vs. WCAG AA Normal Text (4.5:1)
2.96 pts
Margin vs. WCAG AAA Normal Text (7.0:1)
0.46 pts
Margin vs. UI / Large Text (3.0:1)
4.46 pts

WCAG 2.1 Contrast Ratio

Graph 1 • Lighter Relative Luminance Sensitivity Recalculates the domain equation across 50% to 150% of the primary input while holding other parameters constant.
0 : 1 5.9 : 1 11.9 : 1 50%: 3.92 : 1 3.9 50% 75%: 5.69 : 1 5.7 75% 100%: 7.46 : 1 7.5 100% 125%: 9.23 : 1 9.2 125% 150%: 11 : 1 11 150%
Graph 2 • Primary & Supporting Metric Comparison Compares the primary output alongside supporting domain benchmarks.
WCAG 2.1 Contrast Ratio 7.46 : 1 Margin vs. WCAG AA Normal Text (4.5:1) 2.96 pts Margin vs. WCAG AAA Normal Text (7.0:1) 0.46 pts Margin vs. UI / Large Text (3.0:1) 4.46 pts
Graph 3 • Exact Output Table & Units Displays each calculated output in its exact domain unit.
WCAG 2.1 Contrast Ratio7.46 : 1Margin vs. WCAG AA Normal Text (4.5:1)2.96 ptsMargin vs. WCAG AAA Normal Text (7.0:1)0.46 ptsMargin vs. UI / Large Text (3.0:1)4.46 pts
Summary: Relative luminance L₁=0.92 against L₂=0.08 produces a 7.46:1 contrast ratio (Passes WCAG AAA (≥7:1)).
Summary: Relative luminance L₁=0.92 against L₂=0.08 produces a 7.46:1 contrast ratio (Passes WCAG AAA (≥7:1)).
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Formula & Mathematical Methodology: WCAG Contrast Ratio Systems Engineering Formula

ContrastRatio = (max(L₁, L₂) + 0.05) / (min(L₁, L₂) + 0.05)
ContrastRatio = (max(L₁, L₂) + 0.05) / (min(L₁, L₂) + 0.05)
  • lighterRelativeLuminance: Lighter Relative Luminance (L₁ (0–1))
  • darkerRelativeLuminance: Darker Relative Luminance (L₂ (0–1))

Rounding: Binary/decimal capacities and engineering metrics retain full floating-point precision and round to 2 decimal places.

Worked Example: Architecture Sizing Example: WCAG Contrast Ratio

Verify WCAG 2.1 AA (4.5:1) and AAA (7.0:1) text accessibility contrast ratios.

  1. Enter the workload parameters, model dimensions, or network link specifications.
  2. Compute the sizing equation: ContrastRatio = (max(L₁, L₂) + 0.05) / (min(L₁, L₂) + 0.05).
  3. Inspect the primary capacity metric, headroom buffers, and 3 SVG visualizations.
Result: Calculates WCAG Contrast Ratio via ContrastRatio = (max(L₁, L₂) + 0.05) / (min(L₁, L₂) + 0.05).

Frequently Asked Questions

How does the WCAG 2.1 Relative Luminance & AA / AAA Color Contrast Ratio Calculator compute capacity?

It evaluates ContrastRatio = (max(L₁, L₂) + 0.05) / (min(L₁, L₂) + 0.05) directly in your browser and plots three custom SVG diagrams.

Can I compare different cluster or model configurations side by side?

Yes. Use the "Compare (0/3)" button in the results panel to pin up to three configurations.

Does this tool upload any of my architecture parameters?

No. All calculations run 100% client-side in your browser.

Developer Tools · Networking & Digital Systems

WCAG 2.1 Relative Luminance & AA / AAA Color Contrast Ratio Calculator: inputs, method, and how to read the result

Verify WCAG 2.1 AA (4.5:1) and AAA (7.0:1) text accessibility contrast ratios.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Lighter Relative Luminance: Relative luminance of lighter color L₁ (0.00 pure black to 1.00 pure white).
  • Darker Relative Luminance: Relative luminance of darker color L₂ (0.00 pure black to 1.00 pure white).

What the calculation includes

With the default values shown, WCAG 2.1 Contrast Ratio is 7.46 : 1. The calculation follows WCAG Contrast Ratio Systems Engineering Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Lighter Relative Luminance from 0.92 L₁ (0–1) to 1.01 L₁ (0–1) changes WCAG 2.1 Contrast Ratio from 7.46 : 1 to 8.15 : 1. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses industry-standard IEEE, IETF RFC, and GPU/cloud hardware sizing conventions.
  • Capacity planning estimate; benchmark under production traffic patterns before finalizing cluster or hardware procurement.

Scope: IEEE / IETF / Cloud Systems Engineering Standard Check the assumptions and limitations against your situation before relying on the estimate.

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