Abstract-- This paper studies a statistical distribution of instantaneous power in pulse-shaped single-carrier (SC) modulation. Such knowledge is of significant importance to estimate several concerns associated with the non-linearity of power amplifiers, e.g., required back-off level or clipping distortion in amplified signals. However, existing works often rely on MonteCarlo simulations, since analytical derivation of the statistical distribution of SC signals is a complex problem involving combined dependency of a constellation format and a pulse shape. In this paper, we tackle this problem and propose two new analytical methods based on the uniform distribution approximation of discrete signal points. The derived expressions can be easily evaluated and serve as tight upper bounds for high-order pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM).