Cutting Speed Calculator

About this calculator

Cutting speed (also called surface speed, denoted Vc) is the speed at which a cutting tool's edge moves relative to the surface of the workpiece being machined, calculated as Vc = π · D · N / 1000, where D is the diameter (in mm) of the tool (for milling/drilling) or workpiece (for turning), N is the spindle speed in revolutions per minute (RPM), and the result is in meters per minute. It's essentially the tangential velocity of a point on the rotating diameter.

Machinists, CNC programmers and manufacturing engineers use cutting speed to select the correct spindle RPM for a given tool and material combination — every material and tool coating has a recommended cutting speed range (found in machinability tables) that balances tool life against material removal rate. Running too fast overheats and dulls the tool prematurely; running too slow wastes cycle time and can cause poor surface finish or built-up edge. This calculator finds Vc from diameter and RPM, or can be rearranged to find the RPM needed for a target cutting speed.