Why subtract the scrap sale price?

Because scrap you grind is scrap you no longer sell. The gain per kg is the virgin you stop buying, less grinding cost, less what a recycler would have paid you.

What belongs in grinding and handling cost?

Granulator electricity, blade sharpening and screens, operator time to feed and clean it, conveying, and drying the regrind for hygroscopic resins. Divide a year of those costs by the kg ground.

How much regrind can I count?

Only what goes back into parts within the regrind limit. Regrind over the limit, or from another grade or color, still has to be sold or scrapped, so it saves nothing here.

Is simple payback enough to approve a central granulator system?

Not on its own. Payback ignores interest and every saving after the payback date, so for a large system also run net present value on the same annual savings.

Injection Molding calculator

Plastic Regrind Savings Calculator

Find what regrind really saves once grinding cost and lost scrap sales come off, and how fast a granulator pays back. You need regrind volume, resin and scrap prices, grinding cost and a granulator quote.

What this calculator does

Net yearly savings from grinding scrap back into production, and whether the granulator meets your payback hurdle.

Formula used

Net savings per kg = virgin resin price − grinding and handling cost − scrap sale price
Net annual savings = regrind fed back per year × net savings per kg
Granulator payback (months) = installed cost ÷ net annual savings × 12
Regrind needed for the hurdle = installed cost × 12 ÷ (payback hurdle × net savings per kg)

Inputs explained

Regrind Fed Back per Year: Granulator log, or regrind per shot × shots per year.
Delivered Virgin Resin Price: Latest resin invoice price including freight.
Grinding and Handling Cost: Granulator power, blades, labor and conveying per kg ground.
Scrap Sale Price: What a recycler pays per kg; 0 if you landfill it.
Granulator Installed Cost: Quote for granulator, conveying and installation; 0 if owned.
Payback Hurdle: Longest payback your plant accepts on equipment.

How to use the result

Best suited to justifying a beside-the-press granulator, choosing between selling scrap and grinding it, reporting material savings from a closed loop.
Extra rejects caused by regrind are not deducted; if regrind raises scrap, subtract that cost from the net saving. Landfill fees avoided are not credited, so the saving is understated where scrap cannot be sold.

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

Why subtract the scrap sale price? Because scrap you grind is scrap you no longer sell. The gain per kg is the virgin you stop buying, less grinding cost, less what a recycler would have paid you.
What belongs in grinding and handling cost? Granulator electricity, blade sharpening and screens, operator time to feed and clean it, conveying, and drying the regrind for hygroscopic resins. Divide a year of those costs by the kg ground.
How much regrind can I count? Only what goes back into parts within the regrind limit. Regrind over the limit, or from another grade or color, still has to be sold or scrapped, so it saves nothing here.
Is simple payback enough to approve a central granulator system? Not on its own. Payback ignores interest and every saving after the payback date, so for a large system also run net present value on the same annual savings.

Related guides

Last reviewed 2026-10-01.