Plastic Part Weight Calculator

For the hollow cylinder option, Height stops being a vertical dimension and instead becomes wall thickness — the calculator subtracts it from the outer radius (half of Width) to derive the inner radius, then computes the tube's cross-sectional ring area from the difference between the outer and inner circles. If you enter a wall thickness larger than the outer radius, the inner radius is floored at zero rather than going negative, which effectively (and correctly) turns the shape into a solid cylinder.

The engine itself is a straightforward geometric-volume-times-density calculation that applies to any of the three shapes, not a blow-molding-specific simulation — it doesn't model parison thickness variation, blow-up ratio, or the wall-thinning that happens as plastic stretches against a mold in real blow molding. Because real blow-molded hollow parts have wall thickness that varies around the part rather than the uniform thickness this calculator assumes, its hollow-cylinder output is best used as an idealized upper-bound weight estimate, not a precise prediction.

Weight scales exactly linearly with the density figure you enter, since the formula is simply volume (cm³) times density (g/cm³) with no other adjustment — a 10% error in density produces exactly a 10% error in every weight and cost output. Because common resins span a wide range (PP around 0.90 g/cm³ up to PTFE at 2.15 g/cm³, more than double), using the wrong resin's density is the single easiest way to get a materially wrong estimate, so it's worth double-checking the plastic type against the reference values in the input's help text.

Solid, in this context, means uniform material with no internal voids or ribbing beyond the specific shape geometry — the hollow cylinder does subtract out the inner bore, but whatever plastic remains in the ring cross-section is treated as fully dense, with no gas-assist voids, foaming, or wall-thickness variation around the circumference. Real molded parts, especially blow-molded ones, often have thinner or non-uniform walls in practice, so this model tends to overstate weight compared to an actual finished part.