How do you calculate a polymer blend ratio?

Divide the major polymer parts by the minor parts. With 100 parts over 4 parts the raw ratio is 25, meaning 25 parts of the primary polymer per part of the second component.

What does the conversion factor do?

It rescales the raw ratio to a different basis, such as mass to volume. At a factor of 1 the converted ratio equals the raw ratio, so 25 stays 25.

What is a phr in rubber blending?

Parts per hundred rubber is the standard recipe basis. This tool's ratio complements phr by expressing the proportion of one polymer to another rather than to the total rubber.

How do I convert a mass ratio to a volume ratio?

Multiply the mass ratio by the ratio of densities using the conversion factor input. Leaving it at 1 keeps the ratio on the same basis you entered.

Why does my blend ratio differ from the batch card?

Usually the two are on different bases, mass versus volume, or the minor component includes an additive you didn't count. Confirm both numerator and denominator use the same units before comparing.

Does a higher ratio mean more of the main polymer?

Yes. A ratio of 25 means the major polymer dominates heavily; lowering the denominator or raising the numerator pushes the compound further toward the primary elastomer's properties.

Rubber, Tires, Foam & Elastomer Manufacturing calculator

Polymer Blend Ratio Calculator

The polymer blend ratio expresses how two elastomers or a polymer and an additive are proportioned in a compound, and it directly governs the balance of processability, cure and end-use properties. Compounders and R&D chemists use it when co-blending, for example, natural rubber with polybutadiene or SBR to tune abrasion, grip and heat build-up. Expressing the recipe as a single ratio makes it easy to scale a lab batch to a production Banbury and to spot recipe drift across shifts. This calculator divides the two part counts and applies an optional conversion factor so you can move between phr, mass and volume bases.

What this calculator does

Estimate polymer blend ratio for rubber, tires, foam and elastomer manufacturing using production-ready inputs so teams can compare two matched quantities on the same reporting basis.
Use it when polymer blend ratio in rubber, tires, foam and elastomer manufacturing is being indexed against a reference for rubber, tires, foam and elastomer manufacturing reporting.
It divides the major polymer parts by the minor polymer or additive parts, then multiplies by a conversion factor to express the blend on your chosen basis.

Formula used

Polymer blend ratio = polymer blend ratio numerator ÷ polymer blend ratio denominator
Converted polymer blend ratio = ratio × polymer blend ratio conversion factor

Inputs explained

Major polymer parts:
Minor polymer or additive parts:
Ratio conversion factor:

How to use the result

Use it when formulating a co-blend, scaling a lab recipe to production, or auditing whether a batch card matches the target polymer proportion.
It is a pure proportion; it does not account for density differences, so a mass-based ratio will not equal a volume-based one without a proper conversion factor.

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.
U.S. light vehicles sell at a 16.9 million annual rate (BEA, Jun 2026), up 4.1% from a year earlier, the volume signal for automotive supply chains.
The U.S. has 11,391 plastics and rubber products establishments employing about 815,988 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate a polymer blend ratio? Divide the major polymer parts by the minor parts. With 100 parts over 4 parts the raw ratio is 25, meaning 25 parts of the primary polymer per part of the second component.
What does the conversion factor do? It rescales the raw ratio to a different basis, such as mass to volume. At a factor of 1 the converted ratio equals the raw ratio, so 25 stays 25.
What is a phr in rubber blending? Parts per hundred rubber is the standard recipe basis. This tool's ratio complements phr by expressing the proportion of one polymer to another rather than to the total rubber.
How do I convert a mass ratio to a volume ratio? Multiply the mass ratio by the ratio of densities using the conversion factor input. Leaving it at 1 keeps the ratio on the same basis you entered.
Why does my blend ratio differ from the batch card? Usually the two are on different bases, mass versus volume, or the minor component includes an additive you didn't count. Confirm both numerator and denominator use the same units before comparing.

Last reviewed 2026-05-12.