Cutting Speed Calculator
Calculate the surface cutting speed (m/min or SFM) from spindle RPM and tool diameter for turning, milling, and drilling operations.
Results
What is it?
Surface cutting speed (Vc) is the relative velocity between the cutting edge and the workpiece surface. It is independent of tool diameter — two tools of different diameters must run at different RPMs to achieve the same cutting speed. Correct cutting speed ensures optimal tool life, surface finish, and chip formation.
How to use
Select your unit system, enter the spindle RPM and the tool (or workpiece) diameter. For Metric, enter diameter in mm and get m/min. For Imperial, enter inches and get Surface Feet per Minute (SFM). Compare the result against the recommended cutting speed range for your material.
Example scenario
A lathe runs at 1,000 RPM turning a 50 mm diameter steel bar. Vc = (π × 50 × 1000) / 1000 = 157 m/min. For carbon steel, recommended Vc with carbide is typically 100–250 m/min — this is well within the acceptable range.
Pro tip
HSS tooling typically runs at 20–40% of the cutting speeds recommended for carbide. As tool diameter decreases (e.g. small drills), RPM must increase significantly to maintain the same cutting speed. Many CNC controls can apply constant surface speed (CSS) automatically to compensate during turning operations.