This document specifies a method for the determination of the mass per unit area. It also specifies five methods (Method A to Method E) for the determination of the fibre mass per unit area of moulding compounds and prepregs. The five methods are as follows:— Method A: Extraction by Soxhlet;— Method B: Extraction by immersion in solvent in a beaker;— Method C: Decomposition by loss ignition;— Method D: Extraction by wet combustion;— Method E: Method by calculation.This document is applicable to the following types of materials:— moulding compound and preimpregnated unidirectional sheet, tape, fabric and mats;— prepregs in which any type of reinforcement (aramid, carbon, glass, etc.) and any type of matrix (thermosetting or thermoplastic) has been used.Typically, reinforcement fibres are coated with sizing or finishes. These normally dissolve with the resin and are, therefore, included in the resin content.This document is not applicable to the following types of prepregs:— those containing reinforcements which are soluble (or partly soluble) in the solvents used to dissolve the resin.