Technologies are described herein for converting presentations between differing slide dimensions and aspect ratios. During dimensional conversion of a slide, foreground objects placed on the slide by a user are dimensionally scaled and repositioned on the slide based on a change in the overall dimensions of the slide, while background objects on the slide originating from a slide master associated with the slide are replaced with corresponding background objects from a new template associated with the new aspect ratio of the slide. Any content and/or properties of the old background objects on the slide are copied to the corresponding background objects on the dimensionally converted slide.