How do you calculate finished part cost in rotational molding?

Multiply quantity by per-part variable cost by the capture factor, then add fixed cost. For 100 parts at $45 each and 80% capture plus $250 fixed, total cost is $3850 and per-piece cost is $38.50.

What does the capture factor represent?

It is the share of the full variable rate you allocate to this run — 80% here. Use it to strip out costs carried elsewhere or to model a partial allocation, dropping $4500 of gross variable cost to $3600 captured.

Why is per-part cost higher than my resin cost?

Resin is only part of it. Energy for the oven cycle, labor for loading and de-molding, and the $250 fixed setup all fold in, which is why the per-piece figure lands at $38.50 rather than the raw material price.

How much does run size affect rotomolding part cost?

Fixed cost is spread over every part, so small runs cost more per piece. Here $250 across 100 parts adds $2.50 each; across 1000 parts it would add just $0.25.

What is a good per-part cost for a rotomolded product?

There is no universal figure — it depends on part size, resin, and run length. The useful test is whether per-piece cost sits comfortably below your quoted price with margin, which this calculator makes explicit.

Should fixed cost include the mold itself?

Include the amortized share of the mold for this run, not its full purchase price, unless you are recovering the whole tool on one order.

Rotational Molding calculator

Finished Part Cost Calculator

Finished Part Cost rolls the resin, energy, labor, and fixed setup charges of a rotomolding run into a single defensible per-piece number. Estimators and cost engineers use it when quoting a molded part or reviewing whether a job actually cleared its costs. Rotomolding carries heavy fixed charges — mold setup, oven warm-up, and tooling amortization — that hit small runs hardest, so spreading them correctly matters. The capture factor lets you allocate only the share of variable cost that belongs to this job before adding fixed charges.

What this calculator does

Finished Part Cost rolls the resin, energy, labor, and fixed setup charges of a rotomolding run into a single defensible per-piece number.
Use it when finished part cost in rotational molding is being put through a rotational molding weighted-cost review.
It computes total run cost as quantity times per-part cost times a capture factor plus fixed cost, then divides by quantity for per-piece cost.

Formula used

Finished Part Cost cost = quantity × rate × capture factor + fixed cost
Per-unit finished part cost = total cost ÷ quantity

Inputs explained

Parts in the costed run:
Variable cost per part (resin, energy, labor):
Cost capture / allocation factor:
Fixed run cost (setup, mold, tooling):

How to use the result

Use it when quoting a rotomolded part or checking whether a completed run recovered its full cost.
It assumes one blended variable rate per part, so parts with very different wall thickness or resin grades in the same run need separate passes.

Current U.S. benchmarks

The producer price index for plastic resins and materials stands at 319.371 (BLS, May 2026), up 19.5% 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

How do you calculate finished part cost in rotational molding? Multiply quantity by per-part variable cost by the capture factor, then add fixed cost. For 100 parts at $45 each and 80% capture plus $250 fixed, total cost is $3850 and per-piece cost is $38.50.
What does the capture factor represent? It is the share of the full variable rate you allocate to this run — 80% here. Use it to strip out costs carried elsewhere or to model a partial allocation, dropping $4500 of gross variable cost to $3600 captured.
Why is per-part cost higher than my resin cost? Resin is only part of it. Energy for the oven cycle, labor for loading and de-molding, and the $250 fixed setup all fold in, which is why the per-piece figure lands at $38.50 rather than the raw material price.
How much does run size affect rotomolding part cost? Fixed cost is spread over every part, so small runs cost more per piece. Here $250 across 100 parts adds $2.50 each; across 1000 parts it would add just $0.25.
What is a good per-part cost for a rotomolded product? There is no universal figure — it depends on part size, resin, and run length. The useful test is whether per-piece cost sits comfortably below your quoted price with margin, which this calculator makes explicit.

Last reviewed 2026-05-12.