Most codes require specific measurements for the density of a construction grade bale. The code I work with calls for a bale density of at least 7 pounds per cubic foot of material. The bales I use measure 18″ wide x 14″ tall x 45″ long and weigh roughly 50 pounds. Many bales measure 18″ x 14″ x 36″ and weigh between 40 and 45 pounds. These numbers are for two string bales. To calculate the density of the bales I use, follow the formula below:
Multiply 18*14*45 = 11,340 cubic inches
Divide 11,340/1728 = 6.5625 cubic feet
Divide 50 pounds by 6.5625 cubic feet = 7.62 pounds per cubic foot
You can substitute your bale measurements and weight into this equation to calculate the density of your bales no matter what size they are.