---
term: "Hardness Scale Conversion"
category: "material-testing"
shortDefinition: "Empirical relationships between Rockwell, Brinell, Vickers, and Shore hardness scales for metals and plastics; approximate only and material-specific per ASTM E140 guidance."
relatedStandards: ["ASTM E140","ISO 18265"]
url: "https://vectorbtc.com.tr/resources/glossary/hardness-conversion/"
---

## What it measures

**Hardness conversion** maps a result from one **hardness scale** to another using tabulated or fitted correlations. Conversions support specification review when only one scale is certified on site.

## How it is tested

Conversions are **not a test method**—they are calculations applied after a valid hardness measurement on the correct scale, load, and indenter.

## Standards and reporting

ASTM E140 and ISO 18265 emphasize conversions are **approximate**. Always state source equation and material class; prefer direct measurement on the required scale for acceptance.

## Common errors

Applying steel correlations to aluminium, ignoring heat-treatment state, and treating converted values as metrologically equivalent to direct readings.