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Perceived Brightness Calculator - Online Luminance Formula

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Perceived Brightness Calculator

Calculate the perceived brightness of a color using the standard luminance formula. Ideal for accessibility and design decisions.

Color Input
#

Preset Colors:

Brightness Result
0.65
Scale: 0 (black) to 1 (white)

Light Text

Sample Text

White on this color
Contrast ratio: --

Dark Text

Sample Text

Black on this color
Contrast ratio: --

How It Works

The perceived brightness (luminance) of a color is calculated using the standard relative luminance formula from WCAG 2.0, which accounts for human eye sensitivity to different colors:

Y = 0.2126 * R + 0.7152 * G + 0.0722 * B

Where R, G, B are the linearized sRGB values (0–1) after applying gamma expansion. This formula gives a value from 0 (black) to 1 (white), indicating how bright the color appears to the average human eye.

For accessibility, WCAG recommends a contrast ratio of at least 4.5:1 for normal text. Our tool also calculates the contrast ratio against white and black based on this luminance value.

Frequently Asked Questions

Perceived brightness is a measure of how bright a color appears to the human eye, based on the way our eyes perceive different wavelengths. It’s not simply the average of RGB values; green contributes the most, blue the least.

We use the standard sRGB linearization and the WCAG 2.0 relative luminance formula: Y = 0.2126 * R + 0.7152 * G + 0.0722 * B. This is the basis for calculating contrast ratios for web accessibility.

The human eye is most sensitive to green light, which is why green contributes about 71.5% of the perceived brightness. Blue, on the other hand, contributes only about 7% because our eyes are less sensitive to it.

Use the luminance value to determine whether light or dark text will be readable. If the luminance is above 0.179, dark text usually yields better contrast; below that, light text is preferred. Our tool also shows the contrast ratio against black and white to help you meet WCAG standards.

No, HSL's "lightness" or "brightness" (value in HSV) is a simple mathematical transformation and does not account for human perception. Our formula provides a perceptually accurate brightness measure suitable for design decisions.
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