Surface roughness converters

4 converters. Roughness values (Ra, Rz, RMS) between micrometers and microinches, each with the formula and the math worked out with your numbers.

Surface roughness

Microinches to micrometers µin → µm 63 µin = 1.6 µm Micrometers to microinches µm → µin 1.6 µm = 62.99 µin Micrometers to nanometers µm → nm 0.4 µm = 400 nm Mils (thou) to micrometers mil → µm 1 mil = 25.4 µm

Surface roughness units at a glance

Unit	Symbol	In micrometers	Defined as
Micrometer	µm	1	0.001 mm
Microinch	µin	0.0254	0.0254 µm
Nanometer	nm	0.001	0.001 µm
Mil	mil	25.4	0.001 in

This converts the unit only. Ra (average), Rz (peak to valley) and RMS (Rq) are different measurements and aren’t interchangeable; for a typical machined surface RMS ≈ 1.1 × Ra.