Injection molding cost per part, explained

The four components

Per-part price = mold amortization (mold / quantity) + resin (shot weight x price, including runner waste) + press time (cycle / cavities x hourly rate) + labor share. At real volumes the mold share dominates everything else.

Worked example

A 20 g PP part, 15% runner waste, $2.8/kg resin: $0.064 material. 28 s cycle in 2 cavities at $55/hr: $0.21 press. $3,500 mold over 5,000 parts: $0.70. Total ~$1.03 + margin - and the same part at 50,000 units drops toward $0.35.

Cycle time is compounding money

One second off a 28 s cycle saves 3.5% of press cost on every part forever - cooling optimization and hot runners repay themselves at volume. Cavities multiply throughput but also mold price; balance against confirmed demand.

Model your own part

Upload your part to our injection molding calculator - weight and cycle estimated automatically, mold amortized over your quantity, breakeven visible instantly.