Exact bolometric light curves of supernova shock breakouts are derived based on the universal, non relativistic, planar breakout solutions (Sapir et al. 2011), assuming spherical symmetry, constant Thomson scattering opacity, κ, and angular intensity corresponding to the steady state planar limit. These approximations are accurate for progenitors with a scale height much smaller than the radius. The light curves are insensitive to the density profile and are determined by the progenitor radius R, and the breakout velocity and density, v_0 and ρ_0 respectively, and κ. The total breakout energy, E_BO, and the maximal ejecta velocity, v_max, are shown to be E_BO=8.0π R^2κ^-1cv_0 and v_max=2.0v_0 respectively, to an accuracy of about 10%. The calculated light curves are valid up to the time of transition to spherical expansion, t_sph≈ R/4v_0. Approximate analytic expressions for the light curves are provided for breakouts in which the shock crossing time at breakout, t_0=c/κρ_0v_0^2, is