Measure the length and width of your room in feet.
Multiply the length and width together and divide the answer by "7" to determine a proportionate ceiling medallion diameter size in inches.
For a 10-by-14 foot room, for example, your calculation would be: 10 feet x 14 feet = 140 square feet 140 / 7 = 20 inches diameter
Measure the height of your ceiling in feet. Use the diameter for the ceiling medallion calculated based on room width and length if your ceiling stands between 9 and 10 feet tall. Opt for a slightly smaller medallion for shorter ceilings.
Measure the diameter of the lighting fixture below the ceiling medallion in inches. Look for a ceiling medallion close to this size in inches if it closely matches the estimated size from the room calculations.