Injection Molding worked example

Resin Cost Per Part with shot weight per part including runner share of 16 g: a worked example in injection molding

Suppose shot weight per part including runner share falls to 16 g. This page works the full calculation at that level so you can see exactly which result moves and by how much. Calculate material cost per molded part from part weight, runner scrap allocation, and resin price per kilogram.

The inputs for this scenario

  • Shot weight per part including runner share: 16 g (the input this scenario stresses; the baseline uses 32)
  • Resin purchase price: 2.85 $/kg (held at the documented default)
  • Scrap/overage allowance factor: 1.05 x (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Resin cost per part = (Material per part / 1000) x Resin price x Waste factor.
  • Result works out to 47.88 $ at these inputs, and this is the headline figure for the scenario.
  • Base material cost (before waste factor) works out to 47.88 value at these inputs.
  • Multiplier works out to 1 x at these inputs.
  • Factor A x B works out to 45.6 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where shot weight per part including runner share sits at 32 g and the headline result is 95.76 $, this scenario comes in 50% below the baseline at 47.88 $.
  • It computes the per-part resin dollar cost by converting shot weight to kilograms, multiplying by resin price, and applying a waste factor. When the numbers land here, the stressed input is the lever to work; the walkthrough above shows exactly how much each output recovers as it climbs back toward the baseline.

Results at a glance

  • Result: 47.88 $ (headline result)
  • Base material cost (before waste factor): 47.88 value
  • Multiplier: 1 x
  • Factor A x B: 45.6 value

Run it with your numbers

  • To rerun this with your own numbers, open the live Resin Cost Per Part calculator, set shot weight per part including runner share to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.