An apparatus and method are disclosed for dynamic keystone correction. A measurement module measures distances from a projector to each of at least three projected points of a first projected image projected on a first surface with projection angles between each projected point. The at least three projected points are endpoints for at least two vectors with a target ratio of vector lengths. An adjustment module calculates an actual ratio of actual vector lengths of the at least two vectors. The adjustment module further adjusts a first aspect ratio of first projected image until the actual ratio is equivalent to the target ratio.