Plastic Density Chart: Specific Gravity and Weight of Engineering Plastics
Density decides what a machined part weighs, whether it floats, and how much stock a job needs. The chart lists the typical density of the 12 plastics we machine and fabricate, taken from the datasheets for the stock shapes parts are cut from: extruded and compression-molded rod and plate, cast sheet and laminate.
Density of plastics
Typical values, lightest first, not a specification. Each figure is the one on that material’s own page, and its datasheet is linked in the row. Injection-molding resin datasheets can differ slightly from stock shapes, so confirm against the datasheet for the grade you are designing with.
Working out what a part weighs
Weight in pounds is the volume in cubic inches times the lb/in³ figure. A 2″ × 4″ × 12″ block of Delrin is 96 in³ × 0.0509 lb/in³, or about 4.9 lb. For a finished part, use the volume of the part, not the stock it is cut from.
Specific gravity is the same number as density in g/cm³. Anything below 1.0 floats in fresh water; in this chart that is UHMW and HDPE.
For sheet, rod and tube in any size, the plastic weight calculator (opens in new tab) does the arithmetic.
Need a part machined from one of these plastics?
Send us your drawing and we will quote it.