Surface Roughness Ra Estimator Calculator helps machinists estimate theoretical surface roughness during turning based on feed rate and tool nose radius. Enter your cutting parameters to calculate the estimated Ra value in micrometers (µm) and microinches (µin). This free machining calculator provides a quick reference for process planning, tool selection, and surface finish evaluation. Actual results may vary depending on the workpiece material, machine condition, tool geometry, vibration, and cutting conditions.

Input parameters

Calculation unit
Sets both unit selectors below and the main result unit. You can still set each input unit separately.
Distance the tool advances per spindle revolution. Typical finishing: 0.05–0.3 mm/rev.
Insert corner radius. Common sizes: 0.2, 0.4, 0.8, 1.2 mm.