A system for estimating a payload of a bed of a machine, comprising: a torque sensor for determining an output torque from a prime mover; a grade detector for determining an angle of inclination of the machine; a sensor for determining machine acceleration; and a controller configured to: store an angle of inclination threshold; store an inclination rate of change threshold; store an acceleration threshold; store an unloaded mass of the machine in an unloaded condition; determine the output torque from the prime mover; determine the angle of inclination of the machine based upon signals from the grade detector; compare the angle of inclination of the machine to the angle of inclination threshold; determine a rate of change in the angle of inclination; compare the rate of change in the angle of inclination to the inclination rate of change threshold; determine the machine acceleration; compare the machine acceleration to the acceleration threshold; and only if: (a) the angle of inclination of the machine is greater than the angle of inclination threshold; (b) the rate of change in the angle of inclination is less than the inclination rate of change threshold; and (c) the machine acceleration is less than the acceleration threshold, determine an estimate of the payload in the bed based upon the output torque from the prime mover, the angle of inclination of the machine, and the unloaded mass. a torque sensor for determining an output torque from a prime mover; a grade detector for determining an angle of inclination of the machine; a sensor for determining machine acceleration; and a controller configured to: store an angle of inclination threshold; store an inclination rate of change threshold; store an acceleration threshold; store an unloaded mass of the machine in an unloaded condition; determine the output torque from the prime mover; determine the angle of inclination of the machine based upon signals from the grade detector; compare the angle of inclination of the machine to the angle of inclination threshold; determine a rate of change in the angle of inclination; compare the rate of change in the angle of inclination to the inclination rate of change threshold; determine the machine acceleration; compare the machine acceleration to the acceleration threshold; and only if: (a) the angle of inclination of the machine is greater than the angle of inclination threshold; (b) the rate of change in the angle of inclination is less than the inclination rate of change threshold; and (c) the machine acceleration is less than the acceleration threshold, determine an estimate of the payload in the bed based upon the output torque from the prime mover, the angle of inclination of the machine, and the unloaded mass. store an angle of inclination threshold; store an inclination rate of change threshold; store an acceleration threshold; store an unloaded mass of the machine in an unloaded condition; determine the output torque from the prime mover; determine the angle of inclination of the machine based upon signals from the grade detector; compare the angle of inclination of the machine to the angle of inclination threshold; determine a rate of change in the angle of inclination; compare the rate of change in the angle of inclination to the inclination rate of change threshold; determine the machine acceleration; compare the machine acceleration to the acceleration threshold; and only if: (a) the angle of inclination of the machine is greater than the angle of inclination threshold; (b) the rate of change in the angle of inclination is less than the inclination rate of change threshold; and (c) the machine acceleration is less than the acceleration threshold, (a) the angle of inclination of the machine is greater than the angle of inclination threshold; (b) the rate of change in the angle of inclination is less than the inclination rate of change threshold; and (c) the machine acceleration is less than the acceleration threshold, determine an estimate of the payload in the bed based upon the output torque from the prime mover, the angle of inclination of the machine, and the unloaded mass.