Should the press rate include the operator?

Yes, because this page has one conversion line for press and labor together. If one operator tends two presses, add half the burdened wage to each press's hourly rate.

Why can more cavities lower cost even when the mold costs more?

Conversion cost divides by cavities, so doubling cavities at the same cycle and press rate halves press cost per part. The bigger mold pays only if program volume spreads its extra cost thinner than that saving.

Is the margin here my profit?

No: it is target price minus manufacturing cost, before packaging, freight, secondary operations, selling overhead and profit. Compare it with what your quote model loads for those items.

How do rejects change this cost?

Rejects already raise the resin line if you took it from Resin Cost Per Part. Press time spent on rejects is not added here; divide conversion cost by your yield when rejects are significant.

Injection Molding calculator

Molded Part Cost Calculator

Build the cost of a molded part from resin, press time and mold amortization, and see whether it clears the customer's target price. You need resin cost, press rate, cycle time, cavities, tooling per part and the target.

What this calculator does

Manufacturing cost of one molded part from resin, press time and tooling, checked against your target price.

Formula used

Conversion cost per part = press rate × cycle time ÷ 3,600 sec per hr ÷ cavities
Molded part cost = resin cost per good part + conversion cost per part + amortized tooling cost per part
Margin at target price = target piece price − molded part cost
Share of cost = resin, conversion or tooling cost ÷ molded part cost
Parts per hour = 3,600 ÷ cycle time × cavities

Inputs explained

Resin Cost per Good Part: From Resin Cost Per Part, with runner and reject losses.
Press Rate With Operator: Injection Machine Hour Rate plus operator labor per press hour.
Cycle Time: Mold close to mold close, from the press cycle monitor.
Cavities: Cavities running, excluding any blocked off.
Amortized Tooling Cost per Part: From Mold Amortization Cost: mold cost spread over program volume.
Target Piece Price: Customer's target price, or the price you quoted.

How to use the result

Best suited to checking a quote against a customer target price, choosing between more cavities and a faster cycle, should-cost review of a supplier's piece price.
Excludes packaging, freight, secondary operations and selling overhead; the margin row must cover them. Setup, changeover and purge cost per lot are not included; see Mold Changeover Cost.

Current U.S. benchmarks

The producer price index for plastic resins and materials stands at 280.569 (BLS, Aug 2026), up 6.6% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 9,635 plastics product manufacturing establishments employing about 677,302 workers (Census County Business Patterns, 2023).

Common questions

Should the press rate include the operator? Yes, because this page has one conversion line for press and labor together. If one operator tends two presses, add half the burdened wage to each press's hourly rate.
Why can more cavities lower cost even when the mold costs more? Conversion cost divides by cavities, so doubling cavities at the same cycle and press rate halves press cost per part. The bigger mold pays only if program volume spreads its extra cost thinner than that saving.
Is the margin here my profit? No: it is target price minus manufacturing cost, before packaging, freight, secondary operations, selling overhead and profit. Compare it with what your quote model loads for those items.
How do rejects change this cost? Rejects already raise the resin line if you took it from Resin Cost Per Part. Press time spent on rejects is not added here; divide conversion cost by your yield when rejects are significant.

Related guides

Last reviewed 2026-10-01.