(Cf. VDI/VDE 2601; DIN in preparation). The percentage bearing area or, to be more exact, the percentage profile bearing area t_p is the ratio of a profile's bearing length to the reference length of a surface. A distinction is drawn between two values: The percentage microprofile bearing area t_pmi, which is the ratio of the bearing length to the measured length of a roughness profile at depth of cross section c. 

The percentage macroprofile bearing area t_pma, which is the ratio of the bearing length to the measured length of a scanned profile at depth of cross section c. 

The percentage profile bearing curve (Abbot's bearing curve) is the graphic representation of the relationship between the ratio values of the bearing profile length and the horizontal plane of the profile cross section.