There is no list price for a plastic injection mold, because a mold is not a catalogue item — it is a one-off piece of tooling engineered around one specific part, one cavity count and one production volume. What you can do is understand the structure of the number, so that a quotation tells you something instead of just being a figure to negotiate against.
Why There Is No List Price
Every mold is custom work. The cavity count, the steel grade, the gate position, the cooling layout, the ejection method and the tolerance band are all derived from the part geometry and the production forecast. Change any one of those inputs and the price moves — sometimes by a factor of three.
This is why two quotations for what looks like the same part can differ enormously and both be correct. One supplier quoted a two-cavity tool in pre-hardened steel with an edge gate; the other quoted eight cavities in hardened stainless with a hot runner and two sliders. They are not competing offers, they are different products.
The question that gets a useful answer: instead of “how much is a mold for this part”, ask “what does a mold cost at 4 cavities, in 718H, with a cold runner and a T1 in the usual timeframe — and what changes if we go to 8 cavities or add a hot runner”. A supplier can answer that precisely, and you can compare offers on equal terms.
Two Budgets: The Tool and the Part
Buyers who focus only on the mold quotation usually end up paying more. There are two numbers, and they trade off against each other.
| The mold (one-time) | The part (per unit) | |
|---|---|---|
| What it is | A piece of capital equipment, built once for one part | A recurring price, quoted per thousand pieces |
| Driven by | Size, cavity count, steel grade, complexity, surface finish, tolerance | Resin price, shot weight, cycle time ÷ cavities, scrap, packaging |
| When it is paid | Once, before production starts | Every shipment |
| Can it change later | Only by re-cutting steel — expensive | Yes, through cycle time and process tuning |
| Where savings hide | Right-sizing cavity count, standard mold base, DFM before cutting | Wall thickness, cooling, runner design, regrind ratio |
A cheap tool that adds ten seconds to the cycle is a permanent cost on every part you will ever run. Over a program of a few hundred thousand pieces, one extra second of cycle time is worth far more than a small difference in tool price — which is why the comparison has to be total cost, not tool cost:
Total cost = mold price + (part price × volume) + freight + maintenance and spares
What Is Inside a Mold Price
A mold quotation is the sum of engineering, steel, machining time and risk. The distribution below is typical for a two-cavity tool with a cold runner; the shares shift as soon as a hot runner, sliders or a textured finish are added.
| Work element | Typical share | What makes it larger |
|---|---|---|
| Design, DFM and CAM programming | 6–9% | Complex geometry, many slides, several iterations before sign-off |
| Mold base and standard components | 12–17% | Larger base, non-standard plate thickness, premium component brands |
| Cavity and core steel | 9–16% | Higher hardness, larger blocks, stainless or hot-work grades |
| CNC machining (roughing and finishing) | 18–24% | More cavities, deep pockets, hard milling after heat treatment |
| EDM (wire and sinker) | 11–19% | Sharp internal corners, thin ribs, deep ribs, fine detail, texture cavities |
| Fitting, spotting and assembly | 8–11% | Multiple parting surfaces, slides, lifters, tight shut-offs |
| Polishing and texturing | 4–7% | High-gloss SPI grade, large textured areas, hand polishing on deep walls |
| Trial shots and correction | 5–8% | Difficult parts, more T rounds, engineering changes after T1 |
| Project management, overhead, margin | 6–9% | Longer program, more communication and documentation |
Two things are worth noticing in that table. First, the two largest line items are machining time — CNC and EDM together are roughly a third of the price. That is why the number of cavities and the amount of fine detail matter more than the raw weight of steel. Second, design and DFM is one of the smallest lines and one of the largest levers: a review that removes two slides or fixes a parting line costs almost nothing at that stage and saves real money downstream.
The Six Factors That Move the Number
Almost every price difference between two quotations traces back to one of these six. The percentages are indicative and compound — a part that is both larger and more complex moves by both factors, not by the larger of the two.
| Factor | What physically changes | Effect on tool price |
|---|---|---|
| Cavity count | Bigger base, more inserts, more machining and spotting | Each doubling ≈ ×1.6–1.9 |
| Part size / projected area | Larger steel blocks, larger base, heavier press | One base size up ≈ +20–35% |
| Steel grade | Machining hours, heat treatment, polishing time | 718H +10–20%; hardened stainless +30–60%; H13 +40–70% |
| Geometry complexity | Each slide, lifter or split line | ≈ +8–15% per side action |
| Surface requirement | Polishing hours, texture, extra EDM | High gloss +8–15%; deep texture +10–25% |
| Tolerance and Cpk | More EDM passes, in-process gauging, harder steel | Tightening key dimensions ≈ +10–25% |
The two that are usually underestimated
- Surface requirement. A mirror polish is not a finishing step, it is a series of steps — each progressively finer, each done by hand on the cavity. On a textured part, the deeper the grain, the more draft the walls need, which in turn changes the parting line and sometimes forces extra machining.
- Tolerance. A drawing that specifies tight limits on every dimension is the single most common reason a quotation comes back higher than expected. Most moulded features work perfectly at general tolerances; only a handful carry function and deserve to be called out.
How Cavity Count Changes the Math
Cavity count is the biggest single decision in the quotation, and the one most often made by feel rather than arithmetic. The table below uses an index rather than a currency, because the absolute number depends on your part; the ratios are what carry across projects.
| Cavities | Tool cost index | Output at a 30 s cycle | Fits best when |
|---|---|---|---|
| 1 | 100 (baseline) | 120 pcs / hour | Large parts, very low volume, validation |
| 2 | 165–190 | 240 pcs / hour | Medium parts, steady repeat orders |
| 4 | 270–350 | 480 pcs / hour | Small to medium parts, established demand |
| 8 | 450–640 | 960 pcs / hour | Small parts with high, predictable volume |
| 16 | 750–1,100 | 1,920 pcs / hour | Very small parts, consumer volume, long programs |
Why it is not simply double
Going from one cavity to two does not double the tool price, because the base, the design, the CAM programming, the trial shots and the project management are shared. It also does not halve the part price, because the machine still has to cycle, and a larger mold needs a larger press with a higher hourly rate. The real effect sits in between — which is exactly what the 1.6–1.9 multiplier captures.
The break-even test
Whether the extra cavities pay for themselves is a straightforward division:
Extra tool cost ÷ saving per part = number of parts to break even
Run that on your own forecast before specifying cavities. If the answer comes back larger than the volume you can genuinely commit to, the extra cavities are a donation to the mold maker. A four-cavity tool running steadily beats an eight-cavity tool that sits idle half the year — and note that more cavities also means a longer setup, more scrap during tuning, and a higher maintenance burden.
Get a quote you can actually compare
Send us the 3D model, the resin and your annual volume. We will come back with a cavity count, a steel grade and a mold structure recommendation — and state what is included, so you can line it up against other offers. Typically within 24 hours.
Steel Grade and Mold Life
Steel choice is a direct purchase of mold life, and buying more life than the program needs is pure waste.
- Pre-hardened grades such as P20 and 718H, around 30–36 HRC, are the workhorses. They machine quickly, take a good polish and cover most commodity, houseware and consumer programs at roughly 100,000–500,000 shots.
- Hardened stainless grades such as S136 or 1.2083 at 48–54 HRC are specified where the resin is corrosive (PVC, some flame-retardant grades), where optical polish is required, or where a million-plus shots are expected.
- Hot-work grades such as H13 and 8407 handle glass-filled resins, high melt temperatures and abrasive wear. They cost more and are slower to machine, but they are the difference between a tool that lasts and a tool that erodes.
- Surface treatments — nitriding, TiN or DLC coatings — are a cheaper way to extend life on an abrasive job than upgrading the whole block.
The decision rule is volume and resin, not preference. A 718H tool on a 30,000-piece-per-year program is the right buy even if a hardened tool would last longer, because the extra life would never be consumed. Conversely, putting a soft grade into a glass-filled part running at high volume guarantees an early re-cut.
Features That Add Cost
Each of these is legitimate engineering, and each has a price that should appear in the quotation as a line item rather than being buried in a lump sum.
- Sliders and lifters — roughly +8–15% each. They add machining, fitting, a wear surface and a failure mode. If an undercut can be redesigned into a snap feature or handled in assembly, that is usually the cheaper route over the life of the program.
- Unscrewing units — +25–50%. Threaded parts that must demold automatically need a gear train or a hydraulic motor, plus control logic and more maintenance.
- Hot runner systems — +15–30% and up, and the manifold itself is normally a bought-in component. It removes runners, cuts cycle time and saves material, but it only pays back above a volume threshold; on a low-volume tool it is dead capital.
- 2K and multi-material molds — a second injection unit, a rotating platen or a core-back, and two material systems to balance. Structurally a different class of tool.
- Insert molding — loading fixtures, hand-loading time and quality control on insert position, all of which surface in the part price rather than the tool price.
- Conformal cooling — adds build cost for the inserts, but shortens the cycle on thick or hot-spot parts. It is a cost decision that pays back in production, not in the tool.
- Part marking — engraving cavity numbers, date stamps, logos and recycling codes is cheap individually and surprisingly not cheap in total when there are many of them.
How to Read a Quotation
Most disputes about mold cost are not about the number, they are about scope. A quotation that does not state its assumptions cannot be compared with another one. These are the questions worth asking of every offer, including ours:
- Does it state the cavity count, steel grade, mold size and runner type? If not, the price is not a specification.
- Is a DFM report included before steel is cut? This is the single most valuable line in any quotation, and it is often the one that is missing.
- What is excluded? Hot runner, texture, spare parts, freight, trial material, gauges and fixtures are the usual omissions.
- How many trial rounds are included, and what does an extra round cost? One T1 is standard; three or four rounds are normal on difficult parts.
- Is the warranty expressed in shots or in years? Shots is the meaningful unit.
- Is delivery measured at T1 or at final approval? Those can be weeks apart, and the difference matters for your launch plan.
- Is the tool yours, and can it be moved? Ownership and the right to transfer the mold should be explicit.
Where Money Gets Wasted
In our experience reviewing incoming drawings, the same handful of items account for most of the avoidable cost:
- Over-tolerancing. Tight limits applied to every dimension instead of the few that carry function. It multiplies inspection time, EDM passes and reject rate for no functional gain.
- Cosmetic requirements on hidden surfaces. A polish spec on a face that will never be seen is money spent on nothing.
- Too many cavities. Capacity bought for a volume that never arrives.
- Design changes after the steel is cut. A change that costs nothing on a screen costs real money once it means re-machining a hardened cavity.
- Buying life the program cannot use. Hardened steel for a short product life cycle.
- Ignoring draft. Under-drafted walls come back as drag marks, and the fix is a re-cut, not a parameter.
- Skipping DFM. The cheapest money in the whole project is the review that happens before the first cut.
- A tool that does not fit your press. Buying a mold sized for a machine you do not own forces a bigger machine into the part price.
Reducing Cost Without Weakening the Part
There is a real difference between a cheaper mold and a less expensive one. These are the levers that reduce cost without taking strength or function out of the part.
- Right-size the cavity count against a committed forecast, not an optimistic one.
- Remove undercuts where geometry allows — a snap fit or a post-assembly step is often cheaper than a slider.
- Relax tolerances that do not carry function, and keep the tight ones where they matter.
- Use a standard mold base instead of a custom plate arrangement.
- Skip the hot runner below the volume where it pays back.
- Uniform wall thickness — the cheapest cycle-time reduction available, and it doubles as a quality improvement.
- Use a bridge tool for validation and commit to production tooling once the design is settled, rather than cutting a production tool around an unproven design.
- Send complete data up front — 3D model, resin, annual volume, cosmetic requirements and the target market. Every missing input becomes an assumption, and assumptions become change orders.
Most of these are design-stage decisions, which is why the design work itself is worth doing properly: see product design, reverse engineering and DFM and injection mold design and mold building. If the process itself is still unclear, start with our guide to how plastic injection molding works, and for how mold structures differ, the eight classifications of injection molds.
Frequently Asked Questions
Why do quotations for the same part differ so much?
Almost always because they describe different molds. Cavity count, steel grade, runner type, number of slides, surface finish and tolerance band are all variables, and a quotation that does not state them cannot be compared with one that does. When two offers differ by a large multiple, the useful next step is not to negotiate but to ask each supplier to list cavity count, steel grade, mold size, runner type, included trial rounds and exclusions side by side.
Is the cheapest mold the cheapest option overall?
Rarely. The mold is a small part of the total spend once volume is real. A tool built with a longer cycle, fewer cooling lines or softer steel shows up in the part price and in maintenance for the whole program. The comparison that matters is total cost: mold price plus part price multiplied by volume, plus freight and spares.
What drives the price more, the size of the part or the number of cavities?
Cavity count usually moves the number more, because it multiplies steel, machining and fitting while also enlarging the base and the press. Part size matters mainly by pushing the mold base and steel blocks up a size class. Complexity — slides, lifters, unscrewing, texture — is the third axis, and it compounds with both.
Can cavities be added to a mold later?
Sometimes, but it is not a cheap way to plan. Adding cavities means re-machining the base, adding inserts, re-routing cooling and re-qualifying the tool, and in many designs there is no room once the base is cut. Cavity count is far better decided correctly at the start, against a realistic annual volume and cycle time.
Are trial samples included in the mold price?
It depends entirely on the quotation, which is why it belongs on the comparison sheet. Most offers include a first trial round; additional rounds, engineering changes and extra material are commonly charged separately. Ask how many rounds are included and what an additional round costs before placing the order, not after the first samples arrive.
What does a mold warranty normally cover?
Typically workmanship and material defects in the tool itself, expressed in shots rather than years — for example a stated shot count within which the tool is expected to run to specification with normal maintenance. Wear parts, damage from incorrect process settings or from a resin the tool was not designed for, and modifications requested after approval are normally excluded.
