How does the room size and ceiling height determine which crown molding I should purchase?

Some people are of the opinion that the height of a ceiling or the size of a room has everything to do with selecting crown moldings; though an interior designer may suggest otherwise.

When selecting crown molding or cornice molding, it is important not only to imagine what the moldings will look like as part of the room, but what they will do to the overall appearance and transformation of the room. While smaller profiles typically finish a room nicely, larger moldings with different shapes and profiles can change the entire look of the room. Installing a very large cove molding like in a room of any size will give the ceiling a more rounded appearance at the walls. While this application may be used in a large dining room, it would also apply to a small powder room, or bath area; for a less daring approach, a smaller profile like would offer a similar effect, while at the same time adding a bit of detail and definition.

Decorative profiles not only affect the contour of the wall and ceiling, but they also tend to frame and even separate the area in which they are installed; often drawing the eye up, calling attention to the added detail, more so than a simpler profile Designers seem to be moving away from the idea that the size of a room or height of a wall determines the size of the moldings to be installed. One adage still maintained however, is that the height of the baseboards along the bottom of the wall should be chosen to compliment the size of the moldings above. The larger the crown, the larger the baseboard installed below.