RGB to LAB Converter — Free Online Tool

Convert RGB values to CIE L*a*b* instantly — accurate, D65-based conversion with no signup required.

How It Works

Converting RGB to LAB is a three-step process, because RGB and LAB describe color in fundamentally different ways: RGB is device-dependent (tied to how a screen emits red, green, and blue light), while LAB is device-independent and modeled on human vision.

Step 1 — sRGB to linear RGB. Each R, G, and B value (0–255) is normalized to a 0–1 range, then gamma-corrected to remove the sRGB curve. Values above 0.04045 use ((c + 0.055) / 1.055) ^ 2.4; values at or below it are divided by 12.92.

Step 2 — Linear RGB to CIE XYZ. The linear RGB values are multiplied through the standard sRGB-to-XYZ matrix (D65 illuminant) to produce X, Y, and Z tristimulus values, which represent color the way the human eye’s cone cells respond to it.

Step 3 — XYZ to CIE L*a*b*. Each XYZ value is divided by the D65 reference white point (Xn = 95.047, Yn = 100.0, Zn = 108.883), then passed through a cube-root-based function. The results combine into:

• L* — lightness, from 0 (black) to 100 (white)
• a* — position on the green–red axis (negative = green, positive = red)
• b* — position on the blue–yellow axis (negative = blue, positive = yellow)

This tool uses the standard D65 illuminant, the most common reference white point for sRGB-based conversions and the default assumed by most design and color-management software.

LAB vs RGB — What’s the Difference?

RGB describes color the way screens produce it. LAB describes color the way humans perceive it. RGB values are relative to a specific device’s red, green, and blue light output, so the same RGB values can look slightly different across monitors, printers, and color profiles. LAB is device-independent — it’s built to match human visual perception, which is why it’s the standard color space for print production, color-matching, and measuring color difference (Delta E).

Designers and print professionals reach for LAB over RGB in a few specific situations:

• Matching colors across devices or media — converting a digital RGB color to LAB is a common first step before sending it to a print workflow, since print relies on device-independent color space rather than screen-based light.
• Measuring perceptual color difference — LAB’s structure makes it possible to calculate how different two colors actually look to the human eye (Delta E), which RGB math alone can’t do accurately.
• Working across color profiles — because LAB isn’t tied to a specific device’s gamut, it’s used as an intermediate step when converting between color spaces (e.g., RGB to CMYK).

Use Cases

• Color matching for print and packaging — convert a brand’s digital RGB colors to LAB before handing them to a print vendor, so the physical output matches the on-screen intent.
• Design QA and color auditing — compare LAB values across a design system to catch colors that are visually inconsistent even when their RGB codes look unrelated.
• Building Delta E or color-difference tools — LAB values are the required input for calculating perceptual color difference between two colors.

FAQ

What is LAB color space?
LAB (CIE L*a*b*) is a device-independent color space that represents color using three values — L* for lightness, a* for the green-to-red axis, and b* for the blue-to-yellow axis — modeled on how the human eye perceives color rather than how a screen produces it.

What’s the formula for converting RGB to LAB?
RGB is first converted to linear RGB by removing the sRGB gamma curve, then to CIE XYZ using the sRGB-to-XYZ conversion matrix, and finally to L*a*b* using the CIE Lab formula referenced against the D65 white point. The full breakdown is in the “How It Works” section above.

Why is LAB used instead of RGB in design and print?
LAB is used because it’s device-independent, meaning a LAB value represents the same perceived color regardless of the screen or printer producing it — unlike RGB, which is tied to a specific device’s color output. This makes LAB the standard for print color-matching and measuring perceptual color difference.

Is RGB to LAB conversion exact or lossless?
The conversion is mathematically precise for the sRGB color space, but LAB and RGB don’t cover identical gamuts, so converting back and forth (RGB → LAB → RGB) can introduce small rounding differences, especially near the edges of the sRGB gamut.

What white point does this converter use?
This converter uses the D65 illuminant (daylight, ~6500K), the standard reference white point for sRGB and the default used by most browsers, design tools, and color-management systems.