The application of the concept of the representative strain is often used in the stress-strain curve determination from indentation test. A new methodology for determining the representative strain for spherical and for Vickers indentation is presented in this article. The results obtained from this methodology show that there is no universal value of representative strain independent of the mechanical parameters of materials indented by Vickers indentation and spherical indentation. It is also shown that the representative strain, obtained by Vickers or by spherical indentation, is much lower when it is obtained from the relationship between the applied force and the penetration depth, F-h, rather than from the relationship between the applied force and the contact radius, F-a. By choosing the same representative strain value in spherical indentation and in Vickers indentation, the results show that the same constraint factor is obtained. Hence, it is possible to determine a perfect analogy between the two types of indentation. For Vickers indentation, the values of the calculated representative strains show that simultaneous measurement of relationships F-a and F-h allows to characterize the hardening law with two unknown parameters. In the case of the spherical indentation, the identification of a material hardening law from simultaneous measurements relationships F-a and F-h should lead to a more accurate determination of the stress-strain curve.