This Technical Report gives the detailed evaluation of uncertainty for volume measurements according to the Guide to the expression of uncertainty in measurement (GUM). ISO 8655-7 covers non-gravimetric methods of volume measurement. ISO 8655-7:-, Annex A, presents the details of a method that employs removable cells (vials) in a UV/VIS photometer. ISO 8655-7:-, Annex B, presents the details of a method that employs a flow cell fixed in a place in a UV/VIS photometer. This Technical Report covers the uncertainty of measurement of both methods.