A molded plastic part costs between $0.15 and $3.00 to produce once the tool exists, and the tool costs $3,000 to $60,000 before the first shot. Those two numbers are the whole story. Piece price is built from resin, machine time, secondary operations, scrap, packaging, and the molder’s margin. Tooling sits on top as a one-time charge you recover across the run. A 42-gram ABS housing in a two-cavity tool runs about $0.57 per part at the press, and the $26,000 mold adds $0.52 per unit at 50,000 pieces or $0.10 per unit at 250,000.
Volume is the variable that moves everything. Below is the arithmetic that turns a CAD model into a number you can put in a business plan.
The Piece Price Equation
Every molder builds a quote the same way, whether the quote sheet shows it or not:
Piece price = resin + machine time + secondary ops + scrap allowance + packaging + margin
Total unit cost = piece price + (tooling ÷ units produced)
The five components carry different weights depending on the part. On a thin-wall, high-cavity commodity part, machine time dominates. On a thick or glass-filled part, resin dominates. On a part with pad printing, ultrasonic welding, or insert installation, secondary operations can exceed the molding cost outright.
Understanding which component dominates your part tells you where to spend design effort. There is no point shaving grams off a part whose cost is 70% machine time and 20% material.
Component 1: Resin
Material cost is shot weight times price per pound, divided by cavity count, adjusted for regrind.
Shot weight is not part weight. A cold runner tool pushes plastic through a sprue and runner system that gets ejected with the parts and thrown away or reground. Runner mass typically adds 15% to 40% of the total shot on a two-cavity tool, less on high-cavitation tools with balanced layouts, more on small parts where runner volume rivals part volume.
Resin prices in 2026, in bulk truckload or Gaylord quantities:
| Resin | Price per pound | Typical use |
|---|---|---|
| Polypropylene (PP) | $0.75 to $1.15 | Living hinges, closures, housings |
| HDPE | $0.70 to $1.05 | Containers, industrial parts |
| HIPS | $0.95 to $1.35 | Low-cost cosmetic covers |
| ABS | $1.20 to $1.80 | Consumer housings, cosmetic parts |
| PC/ABS | $1.80 to $2.60 | Impact-plus-finish housings |
| Polycarbonate (PC) | $2.00 to $3.10 | Clear parts, high-impact structures |
| Acetal (POM) | $1.80 to $2.70 | Gears, bearings, low-friction parts |
| Nylon 6/6, unfilled | $2.20 to $3.40 | Structural, wear surfaces |
| 30% glass-filled nylon | $2.40 to $3.60 | Stiff structural brackets |
| TPE / TPU | $2.20 to $4.50 | Overmolds, grips, seals |
Prices move with oil and with supply disruption. Get a current quote before you build a cost model around any of these.
Worked example. A 42-gram ABS housing in a two-cavity tool, runner adding 25% to the shot:
- Two parts at 42 g = 84 g, plus 21 g of runner = 105 g per shot
- Per-part material = 52.5 g = 0.116 lb
- At $1.45/lb, that is $0.168 per part
- Regrinding the runner at a 25% blend recovers most of that waste, bringing effective material to about $0.145
Add 3% to 5% back for purge, startup scrap, and color changes and you land near $0.15 per part.
Component 2: Machine Time
Machine rate is the press hourly rate divided by parts per hour. Two things set it: press tonnage and cycle time.
Clamp tonnage is driven by the part’s projected area, which is the shadow the part casts on the parting line. The rule is 2 to 3 tons per square inch for easy-flow resins like PP and PE, 4 to 5 tons per square inch for PC, glass-filled nylon, and anything with high viscosity. A 12-square-inch projected area on a two-cavity ABS tool needs roughly 24 square inches times 3.5 tons, so about 85 tons, and you would run it on a 110-ton or 165-ton press.
Domestic press rates in 2026, running a single operator across two or three machines:
| Press size | Hourly rate |
|---|---|
| 55 ton | $45 to $65 |
| 110 ton | $58 to $85 |
| 165 ton | $70 to $100 |
| 300 ton | $90 to $125 |
| 500 ton | $115 to $165 |
| 750 ton and up | $150 to $240 |
Cycle time is dominated by cooling, and cooling scales with roughly the square of wall thickness. A 2.0 mm wall part cools in a fraction of the time a 4.0 mm wall part needs. Typical cycles:
- 1.0 to 1.5 mm wall, small part: 8 to 16 seconds
- 2.0 to 2.5 mm wall, mid-size housing: 22 to 35 seconds
- 3.5 to 4.5 mm wall, thick section: 45 to 80 seconds
Back to the example. A 28-second cycle on a two-cavity tool produces one part every 14 seconds. At a $75 per hour press rate, that is $0.0208 per second, so $0.292 of machine time per part.
This is where cavitation earns its money. Doubling from two cavities to four does not halve the cycle, but it does halve the machine time per part while adding maybe 2 to 4 seconds of cycle for the larger shot. Four cavities at a 32-second cycle produce one part every 8 seconds, which is $0.167 of machine time. That $0.125 per part saving pays back a $14,000 tooling adder at 112,000 parts.
Component 3: Secondary Operations
Anything that happens after the part drops out of the press gets added on. Common adders per part:
| Operation | Cost per part |
|---|---|
| Degating and deflashing by hand | $0.02 to $0.08 |
| Pad printing, one color | $0.06 to $0.18 |
| Hot stamping | $0.08 to $0.22 |
| Ultrasonic welding, one joint | $0.10 to $0.30 |
| Heat-staking, per stake | $0.03 to $0.09 |
| Insert installation (heat-set brass) | $0.06 to $0.15 each |
| Assembly labor, domestic | $0.45 to $0.90 per minute |
| 100% functional test | $0.15 to $0.60 |
A part with a two-color pad print, four heat-set inserts, and an ultrasonic weld carries $0.70 to $1.20 in secondary operations. That is more than the molding cost. Designers who consolidate a print into a molded-in texture or replace inserts with self-tapping bosses cut real money out of the bill, which is the whole argument behind designing for manufacturability before tooling is cut.
Component 4: Scrap, Packaging, and Margin
Scrap allowance on a well-developed tool runs 1% to 3%. On a difficult part with a cosmetic A-surface and a tight tolerance, 4% to 8% is common in the first six months and improves as the process gets dialed in.
Packaging runs $0.02 to $0.12 per part for bulk-packed items in corrugated with layer pads. Individually bagged or thermoformed-tray packaging runs $0.10 to $0.40.
Molder margin sits between 12% and 25% on the manufactured cost, higher for short runs and difficult parts, lower for long-running commodity work.
The Worked Example, Assembled
The 42-gram ABS housing, two-cavity tool, 28-second cycle, 165-ton press, hand-degated, bulk packed:
| Line item | Cost per part |
|---|---|
| Resin, net of regrind | $0.150 |
| Machine time | $0.292 |
| Degate and inspect | $0.040 |
| Scrap at 2% | $0.010 |
| Packaging | $0.030 |
| Subtotal | $0.522 |
| Molder margin at 18% | $0.094 |
| Piece price | $0.616 |
Call it $0.62. Now add the tool.
| Annual volume | Tooling per unit ($26,000 tool) | All-in unit cost |
|---|---|---|
| 2,500 | $10.40 | $11.02 |
| 10,000 | $2.60 | $3.22 |
| 25,000 | $1.04 | $1.66 |
| 50,000 | $0.52 | $1.14 |
| 100,000 | $0.26 | $0.88 |
| 250,000 | $0.10 | $0.72 |
| 500,000 | $0.05 | $0.67 |
The curve flattens hard after 100,000 units. Below 10,000 units the tool is the product’s entire cost structure, which is the whole reason 3D printing beats molding under a certain volume.
What Pushes the Number Up
Six things account for most quotes that come back higher than an inventor expected.
Undercuts. Every side action, lifter, or collapsible core adds tooling and cycle. A slide adds $2,000 to $6,000 to the tool and 1 to 3 seconds to the cycle.
Cosmetic requirements. An SPI A-2 polish or a specified Mold-Tech texture adds $1,500 to $6,000 in tool finishing and raises scrap rate, because a blemish that would pass on a functional part fails on a cosmetic one.
Tight tolerance. Molding holds about ±0.10 mm on a typical dimension without effort. Asking for ±0.03 mm forces tighter process control, more inspection, and higher scrap, adding 15% to 40% to piece price on that feature.
Color. A custom color match costs $250 to $900 in lab work and carries a 10 to 25 pound masterbatch minimum. Running four colors on one tool means four color changes per campaign, each burning 20 to 60 minutes of press time and 5 to 20 pounds of purge.
Glass fill. Glass-filled resins abrade tool steel. A tool that runs 500,000 shots in unfilled ABS may need core replacement at 150,000 shots in 30% glass-filled nylon, so molders quote hardened steel and price the tool accordingly.
Low annual volume. A molder running your job three times a year eats setup cost each time. Setup is 2 to 6 hours of press time plus a technician, so $400 to $1,500 per run, spread over whatever you ordered.
Getting a Number You Can Trust
Rough estimates from a website calculator are worth what you paid. A real quote requires a 3D model, a 2D drawing with tolerances called out, a resin spec, an annual volume, an order quantity, and a finish spec. The process of assembling an injection molding RFQ takes an afternoon and returns numbers within 10% of what you will pay.
Before you send files to anyone, the idea should already be protected. A $399 patent search against the USPTO patent database tells you whether the concept is clear, and a provisional application establishes a filing date before your CAD leaves your machine. The U.S. Small Business Administration also maintains free counseling programs that help small manufacturers build cost models.
If the total is landing outside what your price point supports, the fix is in the design, not the negotiation. Wall thickness, part count, undercuts, and resin selection move the number 20% to 50%. Molder shopping moves it 5% to 12%. Fix the part first. That work belongs in Enhance’s engineering and prototyping stage, before steel gets cut, and it feeds directly into the full cost breakdown an inventor faces.
FAQ
What is the minimum order quantity for injection molding?
Most domestic molders will run 500 to 2,000 pieces as a first order. Overseas molders usually want 3,000 to 10,000. The floor is not technical, it is economic: setup burns 2 to 6 hours regardless of how many parts you order, so a 200-piece run carries $2 to $7 of setup cost per part.
How much does a single injection molded part cost?
For a small consumer part in the 10 to 60 gram range, $0.20 to $1.20 at the press once tooling exists. Larger parts in the 200 to 800 gram range run $1.50 to $6.00. Add tooling amortization on top, which at 10,000 units on a $26,000 tool is $2.60 per part.
Why is the tooling quote so much higher than the part quote?
Because you are buying a precision machine, not a part. A production mold contains hardened steel cavities and cores machined to within 0.01 mm, a water-cooling circuit, an ejection system, and often slides or lifters. That is 200 to 600 hours of engineering, CNC, EDM, and bench fitting. Tooling cost breaks down by tool class and cavity count, and the range is wide because the drivers are.
Does the resin I pick change the tooling cost?
Yes, in two ways. Abrasive resins like glass-filled nylon force harder steel, which adds 15% to 30% to the tool. Corrosive resins like PVC and some flame-retardant grades force stainless cavities or plated surfaces. Shrink rate also matters: steel is cut oversize by the resin’s shrink factor, so switching from PP at 2.0% shrink to ABS at 0.5% after the tool is cut can render the cavity unusable. Lock the resin before tool design starts, using the tradeoffs covered in choosing plastic materials for production.