Units versus parameters
Ra 1.6 µm is approximately Ra 62.992126 µin. It is not an Rz value. The exact factor is 1 µin = 0.0254 µm.
What to do with a different parameter
Ask for the parameter required by the drawing to be measured or reported under its specified standard and conditions. An average absolute height does not determine profile extremes or the root-mean-square height.
Old N labels
N labels are legacy nominal Ra references. The complete table is maintained on the N-grade page; no process-capability or acceptance class is inferred here.
Swipe to read all columns →
| Input | Output (rounded) | What stayed the same |
|---|---|---|
| Ra 0.8 µm | Ra 31.496063 µin | Ra |
| Ra 1.6 µm | Ra 62.992126 µin | Ra |
| Rz 10 µm | Rz 393.700787 µin | Rz |
| Rz 1000 µin | Rz 25.4 µm | Rz |
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Sources and review scope
Reviewed 23 October 2026. Arithmetic examples are labelled separately from source-table facts and standard scope.
NIST SI Units — Length
International inch definition: exactly 25.4 mm. Other unit values on these pages are derived arithmetic.
Open the original source ↗Mitutoyo roughness fundamentals
Parameter definitions explicitly scoped to JIS B 0601:2013 / ISO 4287:1997, Amd.1:2009; includes historical Rz differences.
Open the original source ↗