This document provides a procedure to validate a calculation tool of spectrophotometric and thermal characteristics of the glass products following EN 410 or EN 673. It provides also the methodology to correctly use measured data in the calculation tool. The following characteristics are included in the scope of this document: light transmittance (tv) light reflectance - both sides (rv, r'v) solar direct transmittance (te) solar direct reflectance both sides (re, r'e) total solar energy transmittance (solar factor or g value) (g) thermal transmittance (U value) in the vertical position The following characteristics are excluded from the scope of this document: UV transmittance (tuv) shading coefficient (SC) general colour rendering index (Ra) thermal transmittance (U value) at angles other than vertical