The Solar Reflectance Index (SRI) is a value that incorporates both solar reflectance and emittance in a single value to represent a material's temperature in the sun.

SRI quantifies how hot a surface would get relative to standard black and standard white surfaces. It is calculated using equations based on previously measured values of solar reflectance and emittance as laid out in the American Society for Testing and Materials Standard E 1980. It is expressed as a fraction (0.0 to 1.0) or percentage (0\% to 100\%).