Estimating a vehicle's driving range by combined processing of measured and calculated range data. A measured range it is adjusted to account for processes not included in the original measurements. These adjustments may include changes in road surface, terrain elevation, aerodynamic drag, or other losses. The resulting model is thus relative to the conditions used in quantifying vehicle range by calculating contributions that either penalize or enhance the measured range. This method is implemented in a software system that can also provide real-time display of the range for both a single trip or a contour that illustrates what the range is for all directions.