ISO 21920 - what the standard means for roughness measurement
ISO 21920 is the new standard for mechanical engineering, design and roughness specifications. Learn more about the motivation for this renewed ISO standard, what does it mean for your daily roughness and form measurements, what do the three parts of the ISO 21920 stand for and how to implement it in quality control – Polytec guides you!
The ISO 21920 represents a central set of rules for roughness profiling replacing and modernizing some of the standards that had been generated decades ago.
Describe your measurement task
How to measure surface roughness using Polytec white-light interferometers
Free testing on your samples - roughness, shape, finish?

The roughness concept – principles of ISO-21920
As shown in previous examples, "roughness" is an abstract term, possibly meaning different things for two different people depending on the perspective or expectations. Join or contact us for our roughness webinar explaining the basic concept of roughness in brief. This shall enable a common understanding.

Download the free ISO 21920 guide
The intuitive tables of the free ISO 21920 guide will show you
- how setting classes Sc1 .. Sc5 define the settings for roughness measurements and evaluation, including S-filter and L-filter settings, section length and evaluation length
- the exact parameters for the various setting classes
- the ISO 21920 terms, which old terms are replaced and with are the corresponding terms for translation

Structure of ISO 21920 standard for profiling
ISO 21920 is a profiling standard, consisting of three parts
- the specification of the surface finish (replaces ISO 1302)
- the terms and parameters like nesting index, R-profile, Ra - Rz... (replaces ISO 4238, 13565-2 and -3)
- the specification operators (replaces ISO 4288).
Some terms and parameters were based on the surface standard ISO 25178, which was first published in 2012. In many cases, surface roughness measurement has decisive advantages over profile-based roughness measurement. The optical and areal measurement of surface roughness is not only optical and contact-free, it also provides a complete image of the surface in a click. This is particularly benefitial, if one cannot assure that specific profiles measured are indeed representative for the whole workpiece surface.