A stated legacy definition
Under the JIS B 0601:2013 / ISO 4287:1997 context in Mitutoyo’s guide, Rz combines the highest peak and deepest valley over the sampling length. This is not presented here as a reproduction of ISO 21920-2.
Older ten-point Rz
Older JIS and ISO 4287:1984 used Rz for ten-point roughness. Do not silently relabel an old report or compare the values without checking the definition.
Rz, Ra and Rt
Ra summarizes average height variation; Rz and Rt involve extrema with their specified interval/evaluation definitions. “Rz 6.3 µm” alone does not establish the interval, measurement setup or functional suitability of a surface.
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Sources and review scope
Reviewed 23 October 2026. Arithmetic examples are labelled separately from source-table facts and standard scope.
Mitutoyo roughness fundamentals
Parameter definitions explicitly scoped to JIS B 0601:2013 / ISO 4287:1997, Amd.1:2009; includes historical Rz differences.
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