Calculator Form
Example Data Table
| Foreground | Background | Ratio | AA Normal | AAA Normal | Best Use |
|---|---|---|---|---|---|
| #111111 | #FFFFFF | 18.88:1 | Pass | Pass | Body text |
| #555555 | #FFFFFF | 7.46:1 | Pass | Pass | Paragraph text |
| #777777 | #FFFFFF | 4.48:1 | Fail | Fail | Large text only |
| #000000 | #EEEEEE | 18.10:1 | Pass | Pass | Forms and labels |
Formula Used
The calculator uses relative luminance and contrast ratio. Each red, green, and blue channel is converted from sRGB into linear light.
Linear channel: if c ≤ 0.04045, use c ÷ 12.92. Otherwise use ((c + 0.055) ÷ 1.055)2.4.
Relative luminance: L = 0.2126R + 0.7152G + 0.0722B.
Contrast ratio: (Lighter luminance + 0.05) ÷ (Darker luminance + 0.05).
Normal AA text needs 4.5:1. Large AA text needs 3:1. Normal AAA text needs 7:1. Large AAA text needs 4.5:1.
How To Use This Calculator
- Select the foreground color for text or icons.
- Select the background color behind the content.
- Enter opacity when the foreground is transparent.
- Enter font size and weight.
- Select AA or AAA as the target level.
- Press the calculate button.
- Review the ratio, pass status, and margin.
- Export the result using CSV or PDF.
Contrast Calculator Article
Why Contrast Matters
Contrast decides how easily visitors read text, icons, labels, and buttons. A clear ratio reduces eye strain. It also helps users with low vision. Designers often judge contrast by sight. That can fail under different screens. This calculator gives a repeatable score.
What The Tool Measures
The tool compares a foreground color with a background color. It converts each channel into linear light. Then it finds relative luminance. The lighter value is divided against the darker value. The final ratio shows how strongly the two colors separate.
Advanced Planning
Use the opacity field when text is not fully solid. The calculator blends the foreground over the chosen background before testing. This makes the result closer to real layout behavior. Font size and weight also matter. Large bold text can pass at a lower ratio than normal body text.
Accessibility Goals
Many teams use AA as a practical baseline. AAA is stricter and gives stronger reading comfort. The tool reports normal text, large text, user interface, and graphic object checks. It also shows the selected target and the margin above or below that target.
Design Workflow
Run this check before finalizing a layout. Test headings, body text, links, badges, form hints, and chart labels. Export the result as a CSV file for spreadsheets. Create a PDF when you need a compact review record. Keep exported files with style guides or client approvals.
Better Decisions
A good ratio does not replace human review. Spacing, line length, glare, screen quality, and content priority still affect readability. Use contrast as the first gate. Then review the page on real devices. Prefer simple combinations that remain readable in daylight, dark rooms, and older displays.
Practical Tip
Do not test only brand colors. Test every state, including hover, disabled, error, success, and focus styles. Small labels and placeholder text need extra care. Icons that communicate meaning should also meet non text contrast guidance.
Common Mistakes
Designers sometimes test only black and white pairs. Real interfaces use overlays, muted labels, shadows, and images. These details change the actual ratio. Always test the final color pair, not a remembered palette value. When images sit behind text, test the darkest and lightest image areas separately too.
FAQs
What does contrast ratio mean?
Contrast ratio measures the brightness difference between foreground and background colors. A higher ratio means stronger separation. Stronger separation usually makes text easier to read.
What is a good contrast ratio?
For normal text, 4.5:1 is a common AA target. For stricter AAA normal text, use 7:1. Large text can pass with lower ratios.
Does font size affect contrast requirements?
Yes. Large text can meet accessibility targets with a lower ratio. This page treats text as large when it is 24 px or larger, or 18.66 px and bold.
Why is opacity included?
Transparent text visually blends with the background. The calculator estimates that blended foreground before measuring contrast. This gives a more realistic result for overlays and muted labels.
Can I use this for icons?
Yes. Meaningful icons and graphic objects often need at least 3:1 contrast. Decorative icons may not need the same check, but important controls should be tested.
Is AAA always required?
No. AAA is stricter than AA. Many sites use AA as a practical baseline. AAA is useful for critical reading areas and high comfort interfaces.
Why does a visual guess sometimes fail?
Human judgment changes with screen brightness, glare, surrounding colors, and monitor quality. A calculated ratio gives a stable result that is easier to document.
What should I export?
Export the final color pair, ratio, target level, pass status, and notes. Keep the file with design reviews, style guides, or client approval records.