We consider the inertial range spectrum of capillary wave turbulence. Under the assumptions of weak turbulence, the theoretical surface elevation spectrum scales with wave number k as I η ∼ k α , where α ¼ α 0 ¼ −19=4, energy (density) flux P as P 1=2 . The proportional factor C, known as the Kolmogorov constant, has a theoretical value of C ¼ C 0 ¼ 9.85 (we show that this value holds only after a formulation in the original derivation is corrected). The k −19=4 scaling has been extensively, but not conclusively, tested; the P 1=2 scaling has been investigated experimentally, but until recently remains controversial, while direct confirmation of the value of C 0 remains elusive. We conduct a direct numerical investigation implementing the primitive Euler equations. For sufficiently high nonlinearity, the theoretical k −19=4 and P 1=2 scalings as well as value of C 0 are well recovered by our numerical results. For a given number of numerical modes N, as nonlinearity decreases, the long-time spectra deviate from theoretical predictions with respect to scaling with P, with calculated values of α < α 0 and C > C 0 , all due to finite box effect. [5]. In special cases of weak (or wave) turbulence, mathematical formulations are more accessible and the cascade spectrum can be obtained as an exact stationary solution of the kinetic equation, which governs the evolution of wave spectrum due to nonlinear resonant interactions.For capillary waves, the framework of weak turbulence theory (WTT) is developed by Zakharov and Filonenko [3] (and reformulated in [6,7]). The isotropic spectrum of surface elevation yields a powerlike solution in the inertial range which is expressed in closed form,