[Table Tennis] Why Rubber Hardness Numbers Can Be Misleading

Contents（目次）

１．Introduction
２．The Reality of Rubber Hardness: How Pimple Structure Defines “Feel”
３．The Current State of Differing Measurement Standards by Manufacturer
Continue to Part 2

１．Introduction

The Limitation of Manufacturer Specs

Have you ever felt that rubber hardness ratings don’t actually help much when choosing new rubber?
Even if two rubbers are both labeled “47.5 degrees,” the actual feel can be completely different.
One major reason is simple:
most hardness ratings only measure the sponge itself.
In reality, impact feel is also heavily influenced by:
- top sheet structure
- pimple thickness
- pimple density

Why Choosing Rubber Is So Difficult

There is no official conversion standard shared between manufacturers.
As a result, hardness numbers cannot be compared directly across brands.
Because of this, many players rely on:
- familiar brands
- online reviews
- recommendations from teammates

Beyond the Numbers

Have you ever bought a rubber that looked perfect on paper, but felt completely wrong in actual play?
This article explains the hidden structural factors behind rubber feel.
Understanding these differences can help you choose equipment more logically and avoid expensive mistakes.

２．The Reality of Rubber Hardness: How Pimple Structure Defines “Feel”

The Limitation of Official Specs

Most manufacturer hardness ratings only measure the sponge itself.
However, the actual feel of a rubber is not determined by the sponge alone.
The structure of the top sheet also has a major influence on how the rubber feels during contact.

The Role of the Top Sheet

As shown in the diagram below, the design of the top sheet greatly changes the overall feel of the rubber.
The most important factor is the structure of the internal “pimples” (pips).
Even when the sponge hardness is identical, differences in pimple structure can completely change the playing sensation.

Pimples as “Support Pillars”

In inverted rubbers, the pimples are hidden underneath the top sheet.
In short pips and long pips, they appear on the surface.
These pimples function like structural support pillars.
They control how force is transferred into the sponge during ball contact.

（1）Difference in “Springiness” Based on Pimple “Thickness”

Pimple Diameter and Rigidity

As shown in the diagrams, the thicker the diameter of the pimples, the more resistant they become to bending upon impact.
This increases the structural rigidity of the pimples as “support pillars”.

Impact on Feel

Because the pimples resist bending, the ball does not “sink” into the rubber as easily.
As a result, the overall impact feel of the rubber is perceived as “Harder,” even if the sponge hardness remains the same.

（2）The Impact of Pimple “Density (Spacing)”

Pimple Density and Flexibility

As shown in the diagram below, thicker pimples resist bending more during ball contact.
This makes the pimple structure more stable and rigid.
In other words, the pimples function like stronger support pillars.

Impact on Feel

Because the pimples bend less, the ball cannot sink deeply into the rubber.
As a result, the rubber feels firmer and harder during contact.
This can happen even when the sponge hardness remains exactly the same.

（3）How Structure Dictates “Perceived Hardness”

What Makes a Rubber Feel Harder

A top sheet with thick, densely packed pimples creates a firmer feel than the sponge hardness number suggests.
Because the structure resists bending, the rubber feels more solid during contact.

What Makes a Rubber Feel Softer

Thin pimples with wider spacing bend more easily during impact.
This allows the ball to sink deeper into the sponge.
As a result, the rubber feels softer and easier to “bite.”

Structural Differences Change Everything

Even when the sponge hardness is identical, differences in pimple thickness and spacing can completely change how a rubber feels.
The actual shape of the pimples also influences the playing feel.

３．The Current State of Differing Measurement Standards by Manufacturer

The Root of the Mismatch

One major reason rubber hardness ratings often fail to match the actual feel is simple:
different manufacturers use different measurement tools (durometers).
In other words, brands are not measuring hardness using the same standard.
Because of this, the same hardness number can feel completely different across brands.

Different Tools, Different Numbers

Several global standards exist for measuring rubber hardness.
The final hardness number changes depending on which measurement system is used.
As a result, directly comparing hardness ratings between brands can be misleading.

（1）Why Hardness Numbers Cannot Be Compared

Why “50 Degrees” Does Not Mean the Same Thing

Just because Brand A and Brand B both label a rubber as “50 degrees” does not mean the actual hardness is identical.
Different brands use different measurement standards.

Different Standards by Region and Brand

German-made rubbers (such as ESN products) typically use “German hardness,” which tends to produce higher numerical values.
Butterfly uses its own proprietary measurement scale, often called the “Butterfly Standard.”
Because these systems are different, the same number can represent a very different feel.

Multiple “Rulers” Exist

In simple terms, each manufacturer uses its own “ruler” to measure hardness.
This is one major reason why cross-brand hardness comparisons are so confusing.

（2）How to Use Online Rubber Reviews

Using Community Reviews as a Guide

The internet is filled with independent rubber comparisons, player reviews, and shop playtest reports.
These reviews can help you understand general trends across different manufacturers.
They are especially useful when comparing rubbers that use different hardness standards.

The Limits of Unofficial Data

However, most online information is still based on personal impressions and unofficial testing.
No official conversion formula exists between different manufacturers.
Online comparisons should never be treated as perfectly accurate.

Use Online Information Carefully

Online reviews are useful as reference material, not as absolute answers.
The final decision should always depend on your own playing style and feeling.
Be careful not to rely too heavily on catalog numbers or online opinions alone.

（3）The Particular Difficulty of “Chinese Rubbers”

The Unique Scale of Chinese Rubbers

Personally, I find the hardness ratings of Chinese rubbers (such as DHS) especially difficult to interpret.
The “39-degree” or “40-degree” ratings used by Chinese brands represent a completely different scale from many other manufacturers.
Because of this, direct comparisons with European or Japanese rubbers can be very misleading.
Simple side-by-side comparisons based only on hardness numbers often do not work well with Chinese rubbers.

【Key Takeaways】

Sponge hardness is not based on a universal standard. Each manufacturer uses its own measurement scale.
Online reviews and test data should be used only as rough reference points.
Hardness numbers alone are not reliable for direct cross-brand comparisons.