A method is presented that can be used for the evaluation of the value of the Earth gravity field at any defined position inside or outside an instrument used for physical or metrological experiments. After a brief presentation of the gravimeters used and the evaluation of their respective uncertainties, we describe in detail the procedure developed to determine the gravitational acceleration g at the point of interest. Finally, a realistic evaluation of the uncertainty budget shows that the method can be used in many metrological applications and especially in all experiments aiming at a new definition of the kilogram by virtual comparison of mechanical and electromagnetic power.In this paper, we denote with g the Earth gravity field or gravitational acceleration, which is the sum of all accelerations felt by a free falling body at the surface of the Earth.