Engineering · Calculator
Surface finish converter.
Exact unit conversion within a roughness parameter; illustrative estimates between parameters. Ra, Rz and RMS are not interchangeable for inspection acceptance. Measure the parameter and filtering specified by the drawing.
Enter any value, see the others
Roughness conversion.
Exact units: 1 µin = 0.0254 µm. The example Rz/Ra = 4 and RMS/Ra = 1.11 ratios are assumptions, not universal conversions; surface profiles with the same Ra can have different Rz and RMS. CLA is a legacy term for Ra.
Send these numbers to a quote →Process attainability
What surface finish each process delivers.
| Process | Ra (µin) | Ra (µm) |
|---|---|---|
| Rough turning / milling | 125–500 | 3.2–12.5 |
| Standard turning / milling | 63–125 | 1.6–3.2 |
| Finish turning / milling | 32–63 | 0.8–1.6 |
| Precision milling | 16–32 | 0.4–0.8 |
| Reaming | 32–63 | 0.8–1.6 |
| Wire EDM (rough) | 63 | 1.6 |
| Wire EDM (single skim) | 16 | 0.4 |
| Wire EDM (double skim) | 8 | 0.2 |
| Wire EDM (4-pass skim) | 4 | 0.1 |
| Cylindrical grinding | 8–32 | 0.2–0.8 |
| Surface grinding | 8–32 | 0.2–0.8 |
| Honing | 4–16 | 0.1–0.4 |
| Lapping | 0.5–4 | 0.013–0.1 |
| Polishing | 1–8 | 0.025–0.2 |
| Electropolishing | 4–16 | 0.1–0.4 |
Keep exploring
Related tools & references
Typical Ra by process and what each finish looks like.
Finish-pass feeds that drive the Ra you can hold.
Pair surface finish callouts with dimensional tolerances.
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