Online total daylight reflectance calculator: V1.0.0

We are pleased to introduce our online total daylight reflectance calculator (V1.0.0, first version). Click the screenshot below to access this online calculator.

Calculation principle

The calculator simply converts an sRGB color (common in screen displays and websites) to a CIEXYZ color, whose Y component is equivalent to the total daylight reflectance of the color (refer to this Wikipedia article for more details).

This calculator calculates total daylight reflectance only and it cannot calculate diffuse and specular daylight reflectances, as the latter two components are dependent on surface finishing, but not on surface color.

The conversion is a theoretical conversion and does not introduce conversion errors. In practice, one needs to manually match a physical color with screen displayed color. This manual process introduces some errors. Nevertheless, this online tools is still useful in estimating the total daylight reflectance of color samples.

20% total daylight reflectance

BCA requires that, for roof surfaces with greater than 20° inclination angle, the total daylight reflectance shall be less than 20% (What is daylight reflectance?). The table below lists 4 colors (grey, red, green, and blue) with close to 20% total daylight reflectance.

If your color is brighter than the 4 colors (except blue color, read the explanation below the table), it is possible that it cannot meet the 20% requirement.

Color typeColor valueTotal daylight reflectanceColor display
GreyRGB (123, 123, 123)
Hex (#7B7B7B)
0.198 (19.8%)
RedRGB (248, 0, 0)
Hex (#F80000)
0.200 (19.8%)
GreenRGB (0, 144, 0)
Hex (#009000)
0.199 (19.9%)
BlueRGB (0, 0, 255)
Hex (#0000FF)
0.072 (7.2%)

Human eyes are less sensitive to blue and red colors, but more sensitive to green and grey colors. In the table above, the total daylight reflectance of the most saturated blue color in the sRGB color space is only with 7.2% of total daylight reflectance.

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