Roughness · Ra ⇄ Rz ⇄ Rt ⇄ RMS ⇄ µm ⇄ µin

Complete surface-finish conversion incl. ISO N grade. Rz ≈ 4·Ra, Rt ≈ 5.5·Ra, RMS = 1.11·Ra.

Ra, Rz/Rt and RMS describe the same surface differently - the conversion is a process-dependent approximation, not a fixed factor. Drawings usually state Rz, calculators often Ra.

Note: all cutting and material values are guide values. The tool or machine manufacturer's recommendations are decisive.

The calculator also runs in the workshop without a connection: app and desktop version