Part Weight Calculator
Calculate the weight of an injection molded part from volume and material density. The calculator accounts for the runner system and automatically computes the material cost per part — a key input parameter for economic calculations and machine selection.
Input Parameters
Results
Fill in the data and click Calculate
ARGUS automatically calculates part weight and passes it to cost calculations, machine selection, and cycle optimization
Part weight is the starting point for dozens of subsequent calculations — ARGUS connects them in one project context, eliminating manual data re-entry.
How do we calculate injection molded part weight?
Part weight is one of the most important process parameters — it determines shot size, machine selection, cycle time, and unit cost. Accurate knowledge of part weight is essential both at the mold design stage and during production optimization. Part weight follows directly from the CAD geometry volume and the density of the selected material.
The calculator uses the basic mass equation — the product of part volume and solid-state material density. It additionally accounts for the runner system weight, which typically represents 5–25% of part weight in cold-runner systems.
m — part weight [g]
V — part volume [cm³]
ρ — material density [g/cm³]
mtotal = m × (1 + r/100)
r — runner system share [%]
Solid-state material density differs from melt density. For part weight calculations we use the solid-state density listed on the material datasheet. Typical values: PP 0.90–0.91 g/cm³, ABS 1.04–1.06 g/cm³, PA6 1.12–1.14 g/cm³, PC 1.20 g/cm³, POM 1.41 g/cm³. Filled materials (GF, CF, talc) have higher density — e.g. PA6-GF30 reaches 1.35–1.40 g/cm³.
Why is part weight critical?
Part weight is an input parameter for many subsequent calculations in the injection molding process. Here are the most important applications:
Shot Size — part weight × number of cavities + runner + cushion
Material Cost — weight × price/kg = dominant component of unit cost
Cycle Time — heavier parts require longer cooling and packing time
Efficiency — weight affects energy consumption and material efficiency
Material cost typically accounts for 40–70% of the unit cost of an injection molded part. Therefore even a small weight reduction (e.g. through wall thickness optimization or material change) can significantly affect production profitability. A typical strategy is to keep wall thickness below 3 mm and use ribbing instead of solid cross-sections.
Part weight optimization
The most accurate part volume is obtained from a CAD model (SolidWorks, CATIA, NX). Without a CAD model you can estimate the volume from overall dimensions and a fill factor (0.15–0.40 for typical injection molded parts). Remember to include ribs, bosses, and fastening features, which can account for 10–30% of part volume.
ARGUS automatically recalculates part weight with every material or geometry change
See it for yourself — book a presentation and discover how ARGUS connects weight calculations with the full project context: material, machine, and production history.