How do you calculate regrind blend rate?

Divide regrind weight by total blend weight and multiply by 100. With 400 lb regrind in a 5,000 lb blend, the rate is 8%.

What is a typical maximum regrind rate?

It varies by product and spec, but 10-25% is common for non-critical profile and many pipe applications, while pressure pipe and food-contact film often cap much lower or bar regrind entirely. At 8% against a 10% cap you have 2 points of headroom.

How much regrind is too much?

Beyond the spec cap or the point where melt strength, color, or impact fails QC. Each reprocessing heat history degrades the polymer, so a blend near its limit leaves no margin for regrind that has already been through multiple passes.

Regrind vs virgin resin: how does the blend affect properties?

Higher regrind lowers material cost but reduces molecular weight and can hurt impact strength, clarity, and surface finish. The blend rate is the lever that balances cost savings against those property losses.

How do I stay under a customer's regrind cap?

Weigh regrind and total blend, compute the rate, and keep it below the cap with a buffer. Here 8% sits 2 points under a 10% cap, giving room for batch-to-batch variation in the regrind feed.

Does the calculator account for regrind quality?

No. It is purely a weight percentage. Two blends at the same rate can behave very differently depending on how many heat histories the regrind carries, so pair the number with melt and QC checks.

Plastics Extrusion - Pipe, Film & Profile calculator

Regrind Blend Rate Calculator

Regrind blend rate is the percentage of a feedstock blend made up of reground, reprocessed material rather than virgin resin. Extrusion process and quality engineers on pipe, film, and profile lines watch it because regrind cuts material cost but degrades melt properties, color, and impact strength as the fraction climbs. Many specs and customer requirements cap regrind, so tracking the actual blend rate against that limit keeps product compliant while capturing scrap value. It converts a hopper recipe into a single, auditable percentage.

What this calculator does

Calculate regrind percentage from regrind pounds and total blend pounds for an extrusion recipe.
Use it when setting regrind levels for pipe, film, sheet, or profile runs while staying inside quality or customer limits.
It computes the percentage of a blend that is regrind by weight and the point gap to your target or maximum allowed rate.

Formula used

Regrind Blend Rate = regrind weight in blend ÷ total blend weight
Gap to target = target or max regrind rate - calculated rate

Inputs explained

Regrind weight in blend:
Total blend weight:
Target or max regrind rate:

How to use the result

Use it when setting or auditing a hopper recipe to capture scrap value without violating a spec regrind cap.
It is weight-based and says nothing about regrind quality, so 8% clean in-house edge trim and 8% multi-heat-history regrind score identically despite very different melt behavior.

Current U.S. benchmarks

The producer price index for steel mill products stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The producer price index for aluminum mill shapes stands at 404.859 (BLS, May 2026), up 36.8% from a year earlier. Quotes priced off last quarter's material cost miss this move.
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 3,569 primary metal manufacturing establishments employing about 354,911 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate regrind blend rate? Divide regrind weight by total blend weight and multiply by 100. With 400 lb regrind in a 5,000 lb blend, the rate is 8%.
What is a typical maximum regrind rate? It varies by product and spec, but 10-25% is common for non-critical profile and many pipe applications, while pressure pipe and food-contact film often cap much lower or bar regrind entirely. At 8% against a 10% cap you have 2 points of headroom.
How much regrind is too much? Beyond the spec cap or the point where melt strength, color, or impact fails QC. Each reprocessing heat history degrades the polymer, so a blend near its limit leaves no margin for regrind that has already been through multiple passes.
Regrind vs virgin resin: how does the blend affect properties? Higher regrind lowers material cost but reduces molecular weight and can hurt impact strength, clarity, and surface finish. The blend rate is the lever that balances cost savings against those property losses.
How do I stay under a customer's regrind cap? Weigh regrind and total blend, compute the rate, and keep it below the cap with a buffer. Here 8% sits 2 points under a 10% cap, giving room for batch-to-batch variation in the regrind feed.

Last reviewed 2026-05-12.