How do you calculate scrap resin cost?

Multiply annual resin consumption by the scrap rate (as a decimal) by the delivered resin price. With 50,000 kg/year, a 3% scrap rate, and $2.85/kg, that's 50,000 x 0.03 x 2.85 = $427,500 per year.

What counts as non-recoverable scrap resin?

Material you cannot regrind and reuse: purge during color or material changes, contaminated rejects, degraded startup shots, and runner systems on resins that don't tolerate regrind (or where regrind isn't allowed for a customer spec).

What is a good scrap rate for injection molding?

World-class molders run total scrap (including regrindable) under 2-3%, with non-recoverable scrap often below 1%. A 3% non-recoverable rate like the default is common but leaves real money on the table.

Why is scrap resin cost so high even at a low percentage?

Because resin volume is large. At 50,000 kg/year and $2.85/kg you're buying $142,500 of resin, so even 3% non-recoverable is $427,500 over the modeled period — small percentages on big spend are big dollars.

Does this include regrind savings?

No. This figure is non-recoverable scrap only. If you regrind sprues and runners back into the process, exclude that tonnage from the scrap rate so you don't double-count material you actually reuse.

How can I reduce scrap resin cost?

Cut purge with sequenced color changes and purge compounds, convert cold runners to hot runners, tighten process windows with scientific molding, and dry resin correctly to avoid splay and brittleness rejects.

Injection Molding calculator

Scrap Resin Cost Calculator

Scrap resin cost is the dollar value of plastic that never ships as a good part — purge, sprues and runners that can't be reground, startup shots, and rejected moldings. Molding plant managers and continuous-improvement engineers track it because resin is typically 60-70% of an injection-molded part's cost, so a point of scrap eats directly into margin. This calculator converts a scrap percentage into the hard annual number that justifies a dryer upgrade, a hot-runner retrofit, or a regrind program. Run it monthly and you can see whether a process change actually moved money.

What this calculator does

Calculate the annual cost of scrapped resin from rejects, purging, startup waste, and non-recoverable material.
Use this to quantify material waste costs for lean manufacturing reports, justify quality improvements, or compare scrap costs across molding cells.
It computes the annual dollar cost of non-recoverable resin scrap from your throughput, scrap rate, and delivered resin price.

Formula used

Annual scrap cost = Resin consumption x (Scrap rate / 100) x Resin cost per kg
Track monthly to measure improvement from process or quality changes

Inputs explained

Annual resin throughput across all presses:
Non-recoverable (purge, runner, reject) scrap rate:
Delivered resin price:

How to use the result

Use it when building a scrap-reduction business case, setting a plant scrap-cost KPI, or quantifying the payback on capital like hot runners or closed-loop dryers.
It only values the resin itself — it ignores the machine time, labor, energy, and lost capacity tied up in scrapped shots, so true scrap cost is higher than this figure.

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 scrap resin cost? Multiply annual resin consumption by the scrap rate (as a decimal) by the delivered resin price. With 50,000 kg/year, a 3% scrap rate, and $2.85/kg, that's 50,000 x 0.03 x 2.85 = $427,500 per year.
What counts as non-recoverable scrap resin? Material you cannot regrind and reuse: purge during color or material changes, contaminated rejects, degraded startup shots, and runner systems on resins that don't tolerate regrind (or where regrind isn't allowed for a customer spec).
What is a good scrap rate for injection molding? World-class molders run total scrap (including regrindable) under 2-3%, with non-recoverable scrap often below 1%. A 3% non-recoverable rate like the default is common but leaves real money on the table.
Why is scrap resin cost so high even at a low percentage? Because resin volume is large. At 50,000 kg/year and $2.85/kg you're buying $142,500 of resin, so even 3% non-recoverable is $427,500 over the modeled period — small percentages on big spend are big dollars.
Does this include regrind savings? No. This figure is non-recoverable scrap only. If you regrind sprues and runners back into the process, exclude that tonnage from the scrap rate so you don't double-count material you actually reuse.

Last reviewed 2026-05-12.