Knowing your cost per part determines whether a project is profitable or a margin killer. Injection molding expenses vary wildly depending on tooling, material, volume, and complexity—and most business owners underestimate one or more of these factors. This guide breaks down the real numbers so you can quote accurately and stay competitive.
The Two-Cost Reality: Tooling vs. Per-Part Production
Injection molding splits into fixed costs (the mold itself) and variable costs (what it takes to make each piece). Your total cost per part = (mold cost ÷ total units produced) + material cost + labor + overhead + shipping. This means a $50,000 mold amortized across 100,000 units adds just $0.50 per part—but across 10,000 units, it's $5.00 each.
Most injection molders quote tooling separately because it's a one-time investment that can range from $3,000 for simple single-cavity molds to $100,000+ for complex multi-cavity tools with tight tolerances and custom cooling lines.
Breaking Down Mold Costs
Cavity count and complexity matter most. A single-cavity mold for a basic plastic housing costs $5,000–$15,000. Multi-cavity molds (4, 8, or 16 cavities) cost more upfront but dramatically lower per-part cost at volume. A 16-cavity mold might run $40,000–$80,000 but cuts your per-unit amortization to pennies on high-volume runs.
Material selection also drives mold cost. Polyethylene and polypropylene are cheaper to mold than engineering plastics like PEEK or nylon, which require tighter temperature control and more durable steel. Tolerances tighter than ±0.005 inches add 20–40% to mold expense.
Lead time for molds typically ranges 4–8 weeks for standard tooling, longer if you're pushing material limits or require insert molding.
Variable Costs Per Unit
Once the mold exists, each part's cost breaks down as follows:
- Raw material: $0.50–$3.00+ per part depending on polymer (PP/PE at the low end; engineering plastics much higher)
- Machine time: $0.30–$1.50 per part based on cycle time (10–90 seconds is typical) and machine hourly rate ($40–$150/hour for standard equipment)
- Labor: $0.10–$0.50 per part for trimming, inspection, and packaging
- Overhead/utilities: $0.20–$0.60 per part
- Scrap allowance: Budget 2–5% for first articles and quality rejects
A simple part in basic plastic at 50-second cycle time might cost $1.20–$2.00 to produce. A complex multi-material part with inserts and tight tolerances could hit $4.00–$6.00.
How Volume Changes the Equation
This is where the math either works or doesn't.
| Production Volume | Mold Amortization | Total Est. Cost/Part | |---|---|---| | 5,000 units | $10 (assuming $50K mold) | $11.50–$13.00 | | 25,000 units | $2 | $3.50–$5.00 | | 100,000 units | $0.50 | $2.00–$3.50 |
Anything under 1,000 units rarely makes economic sense for injection molding—hand assembly, 3D printing, or thermoforming may be better. Beyond 100,000 units, multi-cavity molds and automated secondary processes justify higher upfront investment.
Hidden Costs to Factor In
- Prototyping and design iteration: Expect $2,000–$10,000 before committing to production tooling
- Quality/testing: Compliance costs (FDA, UL, RoHS) add $1,000–$5,000 depending on industry
- Secondary operations: Molding + assembly, pad printing, or ultrasonic welding can double per-part cost
- Logistics: Packaging, palletizing, and freight for heavy parts can add $0.50–$2.00 per unit
Setting Competitive Pricing
Your quote should be: (per-part cost × 1.15–1.25 for scrap) + overhead markup (15–35%) + profit margin (20–40%). If competitors are undercutting you significantly, ask about their volume commitments, mold ownership, and whether they're pricing for sustainability or just trying to fill capacity.
Listing your services on Mercoly—with clear pricing tiers, turnaround times, and MOQ thresholds—helps prospects find you, compare options directly, and places your quotation in front of serious manufacturers looking to outsource.
Frequently Asked Questions
Q: At what production volume does injection molding beat 3D printing? Break-even typically occurs between 500–2,000 units depending on part size and material; below that, 3D printing or low-volume urethane casting is cheaper.
Q: Should I own the mold or does the customer? Customer ownership protects intellectual property but shifts risk; mold ownership lets you amortize costs across multiple customers and retain leverage.
Q: How accurate is a cost estimate before tooling? Very accurate (±10–15%) if based on detailed geometry, material, and volume—but always include a contingency because tolerances, insert complexity, or material behavior can shift costs by 20–30% once the mold is running.
Start tracking your actual per-part costs against your estimates to build a benchmarking database that sharpens your quotes over time.