This part of ISO 10300 specifies the basic formulae for use in the determination of the surface load capacity of straight and helical (skew), zerol- and spiral-bevel gears, and includes all the influences on surface durability for which quantitative assessments can be made. This part of ISO 10300 is applicable to oil-lubricated transmissions, as long as sufficient lubricant is present in the mesh at all times. The formulae in ISO 10300 are valid for bevel gears with teeth where the transverse contact ratio is eva < 2. The results are valid within the range of the applied factors as indicated in ISO 10300-1, and in ISO 6336-2. However, the formulae in this part of ISO 10300 are not directly applicable in the assessment of certain types of gear-tooth surface damage, such as plastic yielding, scratching, scuffing or any other type not specified.