Styrene is a small aliphatic hydrocarbon often derived from petroleum distillates. It is commonly polymerized into Styrofoam and made into disposable housewares or made into large sheets. In either case, it is a good insulator. The large sheets are often hung on walls to insulate spaces within buildings or around the outside to insulate the whole building. Knowing the weight of the sheets is important in selecting the proper anchor for hanging the sheets.
Identify the density of the sheet. It is generally printed on the side by the label and other information. It should look like "X kg/ cum." or "X lbs./cft" where X is a number. The first example is the metric version with kilograms per cubic meter. The second example is the standard version with pounds per cubic foot.
Calculate the volume of the sheet. If the density is in metric, the volume should be calculated in cubic meters (length in meters times width in meters times thickness in meters). If the density is in standard, the volume should be calculated in cubic feet (length times width times thickness in inches divided by 1,728).
Multiply the volume by the density to calculate the weight of the sheet.