The weight of a bronze plaque can be estimated by calculating the plaque's volume in inches (height x width x depth) x .31. For smaller plaques (under 36" x 30") allow .25" as the approximate depth. Use .375" for plaques over 36" x 30".
Example: For a 12" x 12" plaque calculate 12" x 12" x .25" = 36 cu. inches x .31 = 11.16. The plaque's estimated weight would be 11 lbs.
An aluminum plaque is approximately 1/3rd the weight of a comparable sized bronze plaque. In the above example, simply divide the answer by 3. A 12" x 12" aluminum plaque weighs approximately 3.6 lbs.
Note: The weight calculation formula above is only an estimate of what your plaque might weigh. Actual plaque weights may vary slightly from casting to casting.