Depth-sensing indentation measurements were performed using the three trihedral pyramid indenters with the specific inclined face angles Ξ² B (Ξ² B = 11.4 β’ , 24.7 β’ (Berkovich) and 43.7 β’ ), three tetrahedral pyramid indenters with Ξ² V (Ξ² V = 10 β’ , 22 β’ (Vickers) and 40 β’ ) and a Knoop indenter (Ξ² K = 25.2 β’ ). The materials tested ranged from ductile metals to brittle ceramics, including soda-lime glass, Si 3 N 4 , MgO, copper/zinc alloy, and high-carbon chromium bearing steels. The loading paths were conformed to the quadratic relations of P = k 1 h 2 , and the unloading paths were well approximated with P = k 2 (h-h r ) 2 , in terms of the indentation load P, penetration depth h, and the residual depth h r of impression. All of the indentation-related parameters were calculated from the loading/unloading P-h hysteresis curves, and then correlated well with the nondimensional plastic strain E tan Ξ² C /H (elastic modulus E , true hardness H and the inclined face angle Ξ² C of equivalent cone indenter). The concept of "equivalent cone" provided an efficient analytical method, by which all of the indentation behaviors for the Vickers-type, Berkovich-type and the Knoop indenters were described in a unified manner. The quadratic approximation for the unloading path combined with the concept of "effective shape of indenter" was successfully utilized to estimate the elastic modulus E of the materials indented.