Weight vs Volume When Mixing

Spray foam material is packaged, sold and shipped on the basis of weight. Therefore, in order to figure the volume of a product packaged in the drum, converting the weight of the product within the drum into gallons is required. To do so, the specific gravity or weight per gallon of material is required information. There is likely to be a difference between manufactures, so confirm with the product supplier to provide this info or if a scale is available, weigh the container first. Specific Gravity and per gallon weight of the liquid for some manufactures are provided on the SDS or product data sheet (formerly MSDS).

  1. When the weight of one gallon of product is known, divide the weight (in pounds) of one gallon of the product by 8.33 lbs. (the weight of one gallon of water). This will provide the specific gravity.
  2. When the specific gravity is known, multiply the specific gravity by 8.33 (the weight of one gallon of water). This will provide the weight of one gallon of the product.
  3. Utilize one of the two following equations to figure how much volume in gallons is in the container:




Many manufactures have made the necessary calculations and have adjusted the drums accordingly while others have not. So, a little due diligence on our part will provide the necessary info to determine how the products are packaged and aid when confirming stroke counter limits.

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John Davidson is the VP of Operations at SprayWorks Equipment Group and is an SPFA PCP Certified Roofing and Insulation Installer, Roofing and Insulation Project Manager, and Supplier Rep. With over 30 years of experience in the spray foam and polyurea industry, John brings a wealth of knowledge and hands-on experience. He has worked on commercial and residential buildings, bridges and infrastructure.

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