Preview Text
This is what your text looks like on this background. The quick brown fox jumps over the lazy dog.
Smaller text is harder to read —make sure you check the WCAG standards below.
Quick Presets
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Key Features
Everything you need, right at your fingertips. Simple, fast, and built for everyone.
WCAG 2.1 Compliant
Checks against official AA and AAA accessibility standards.
Ratio Calculation
Precise contrast ratio calculation using the WCAG formula.
Color Pickers
Choose foreground and background colors with visual pickers.
Hex Input
Enter HEX color codes directly for precise color values.
How to Use This WCAG Contrast Checker
Getting started is easy. Just follow these simple steps.
Pick Colors
Enter or select foreground text and background colors.
View Ratio
See the exact contrast ratio calculated instantly.
Check Standards
See if it passes WCAG AA and AAA for normal and large text.
Adjust if Needed
Tweak colors until you meet accessibility requirements.
About This Color Contrast Checker
Color contrast is the difference in lightness and color between foreground text and its background. Sufficient contrast is essential for readability and accessibility, ensuring that text is readable by people with various visual abilities and in different viewing conditions.
The Web Content Accessibility Guidelines (WCAG) define specific contrast ratio requirements: a minimum of 4.5:1 for normal text (16px or smaller) and 3:1 for large text (18px or larger, or bold 14px+) for AA compliance. AAA compliance requires 7:1 for normal text and 4.5:1 for large text.
Good color contrast benefits everyone, not just people with visual impairments. It improves readability in bright sunlight or on low-quality displays, reduces eye strain during long reading sessions, and makes content more usable for older adults and people with temporary vision issues.
A color contrast checker lets you test text and background color combinations to see if they meet WCAG accessibility standards. It is an essential tool for web designers, developers, and anyone creating digital content who wants to ensure it is accessible to the widest possible audience.
Frequently Asked Questions
What is WCAG?
WCAG (Web Content Accessibility Guidelines) is an international standard for making web content more accessible to people with disabilities. It defines contrast ratios for text to ensure readability for users with low vision or color blindness.
What's the difference between AA and AAA?
AA (minimum) requires a 4.5:1 contrast ratio for normal text and 3:1 for large text (18pt+ or 14pt+ bold). AAA (enhanced) requires 7:1 for normal text and 4.5:1 for large text. Most accessibility laws require AA compliance. AAA is recommended for better accessibility.
How is contrast ratio calculated?
Contrast ratio is calculated using the relative luminance of each color. Relative luminance is measured using the formula (L1 + 0.05) / (L2 + 0.05), where L1 is the lighter color and L2 is the darker color. Luminance is computed from sRGB values using a specific formula defined in the WCAG specification.
How do you calculate time difference?
To calculate the difference between two times, subtract the start time from the end time. If the minutes go negative, borrow 1 hour (60 minutes). If crossing midnight, add 24 hours to the end time. For example, from 22:30 to 02:15 = (26:15 - 22:30) = 3 hours 45 minutes.
What is a unit of measurement?
A unit of measurement is a standard quantity used to express a physical quantity. Standard units like the metric system ensure consistency and comparability across different locations and contexts. The International System of Units (SI) is the most widely used system worldwide.
Why is the metric system better than imperial?
The metric system is decimal-based, making conversions much simpler by multiplying or dividing by 10, 100, 1000, etc. It is also more universally adopted, with almost every country in the world using it officially, making international communication and trade easier.
How do I convert units manually?
To convert units manually, find the conversion factor between the two units and multiply or divide accordingly. When converting from a larger unit to a smaller one, multiply. When converting from smaller to larger, divide. Always double-check your answer for reasonableness.
What are the seven base SI units?
The seven base SI units are: meter (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), and candela (luminous intensity). All other units are derived from these seven base units.
How accurate are online unit converters?
Online unit converters use precise conversion factors and are highly accurate for most practical purposes. Standard conversion factors are internationally defined and constant. However, for scientific or engineering work requiring extreme precision, always verify with authoritative sources.
What is dimensional analysis?
Dimensional analysis is a method of checking calculations by ensuring units of measurement are consistent on both sides of an equation. It can also be used to convert between units using conversion factors. This technique is widely used in physics, engineering, and chemistry.
Why is it important to use the right units?
Using the wrong units can lead to costly errors, miscommunication, and safety hazards. In construction, medicine, aviation, and space travel, unit errors have caused serious incidents and accidents. Always double-check units and clearly label them in all calculations and communications.
How do you calculate time difference?
To calculate the difference between two times, subtract the start time from the end time. If the minutes go negative, borrow 1 hour (60 minutes). If crossing midnight, add 24 hours to the end time. For example, from 22:30 to 02:15 = (26:15 - 22:30) = 3 hours 45 minutes.
What is a unit of measurement?
A unit of measurement is a standard quantity used to express a physical quantity. Standard units like the metric system ensure consistency and comparability across different locations and contexts. The International System of Units (SI) is the most widely used system worldwide.
Why is the metric system better than imperial?
The metric system is decimal-based, making conversions much simpler by multiplying or dividing by 10, 100, 1000, etc. It is also more universally adopted, with almost every country in the world using it officially, making international communication and trade easier.
How do I convert units manually?
To convert units manually, find the conversion factor between the two units and multiply or divide accordingly. When converting from a larger unit to a smaller one, multiply. When converting from smaller to larger, divide. Always double-check your answer for reasonableness.
What are the seven base SI units?
The seven base SI units are: meter (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), and candela (luminous intensity). All other units are derived from these seven base units.
How accurate are online unit converters?
Online unit converters use precise conversion factors and are highly accurate for most practical purposes. Standard conversion factors are internationally defined and constant. However, for scientific or engineering work requiring extreme precision, always verify with authoritative sources.
What is dimensional analysis?
Dimensional analysis is a method of checking calculations by ensuring units of measurement are consistent on both sides of an equation. It can also be used to convert between units using conversion factors. This technique is widely used in physics, engineering, and chemistry.
Why is it important to use the right units?
Using the wrong units can lead to costly errors, miscommunication, and safety hazards. In construction, medicine, aviation, and space travel, unit errors have caused serious incidents and accidents. Always double-check units and clearly label them in all calculations and communications.
About Units and Measurement
Units of measurement are fundamental to science, engineering, commerce, and daily life. They allow us to quantify the physical world, compare values, and communicate measurements accurately. Without standardized units, there would be confusion and chaos in everything from construction to cooking.
The metric system, officially known as the International System of Units (SI), is the most widely used measurement system in the world. Its decimal-based design makes conversions incredibly simple —just multiply or divide by powers of ten. This elegant simplicity is why almost every country has adopted it as their official system.
Time is the most precisely measured physical quantity. Modern atomic clocks are so accurate they lose only about one second every 100 million years. This precision enables technologies like GPS navigation, high-speed internet, and experiments that test the fundamental laws of physics.
Converting between units correctly is important in everyday life. Whether you are following a recipe from another country, planning a road trip abroad, or calculating medicine dosages, getting the conversion wrong can have serious consequences. Always double-check your work and use reliable conversion references.
Understanding scale and units helps you develop intuition about the world. Knowing roughly how much a kilogram weighs, how long a meter is, and how hot different temperatures feel makes you better at estimating, comparing, and making decisions without needing to measure everything precisely.