This paper offers a unified measure for dynamic stability of off-road vehicles that accounts for the tendency to tipover, slide, or loose contact with ground during static equilibrium and in motion. The contacts between the vehicle and ground are assumed rigid, and all wheels are assumed active. The dynamic stability measure is determined by computing the range of velocity and acceleration of the vehicle's center of mass that satisfies a set of dynamics constraints. The upper velocity limit serves as a dynamic stability measure, whereas the acceleration limit at zero speed serves as a static stability measure. In this paper, we demonstrate the approach for a four-wheel drive planar vehicle.