Spindle Speed Calculator


About Spindle Speed Calculator (Formula)

A “Spindle Speed Calculator” is a tool used to calculate the rotational speed of a cutting tool or spindle on a machine tool, such as a lathe or milling machine. The spindle speed is a critical parameter in machining operations as it determines the rate at which the cutting tool engages with the workpiece. This calculator is essential for machinists, engineers, and manufacturers to optimize cutting conditions and achieve desired results. The formula for calculating spindle speed provides insights into the relationship between cutting speed, tool diameter, and the number of cutting edges.

The formula for calculating Spindle Speed is:

Spindle Speed (N) = (Cutting Speed * 1000) / (π * Tool Diameter)


  • Spindle Speed (N) is the rotational speed of the spindle in revolutions per minute (RPM).
  • Cutting Speed is the speed at which the cutting tool travels across the workpiece surface, usually in meters per minute (m/min) or feet per minute (ft/min).
  • π (pi) is a mathematical constant approximately equal to 3.14159.
  • Tool Diameter is the diameter of the cutting tool in millimeters (mm) or inches (in).

This formula calculates the spindle speed required to achieve a specific cutting speed with a given tool diameter.

For example, if the cutting speed is 100 meters per minute and the tool diameter is 20 millimeters, the spindle speed would be:

Spindle Speed (N) = (100 m/min * 1000) / (π * 20 mm) ≈ 1591 RPM

This means that the spindle should rotate at approximately 1591 revolutions per minute to achieve a cutting speed of 100 meters per minute with a 20-millimeter tool.

The Spindle Speed Calculator is used in machining operations to optimize cutting conditions, enhance tool life, and achieve desired surface finish and material removal rates.

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