Cutting Speed to rpm Converter

Convert Cutting Speed to RPM instantly.

Free online converter with accurate results and clear explanations.

Last updatedHow we build & check our tools

How This Tool Works

This converter calculates spindle speed from cutting speed and the tool or workpiece diameter. For metric inputs, it uses RPM = (cutting speed × 1000) / (π × diameter), where cutting speed is in m/min and diameter is in mm.

For imperial machining values, the equivalent formula is RPM = (SFM × 12) / (π × diameter in inches). The calculator converts units before solving, so metric and imperial inputs stay consistent.

For example, 60 SFM with a 2-inch tool gives about 115 RPM: (60 × 12) / (π × 2) = 114.6.

Why This Matters

Accurate spindle speed helps preserve tool life, control heat, and produce a better surface finish. Too much RPM can overheat the tool or workpiece, while too little RPM can cause rubbing, chatter, and poor chip formation.

  • Material choice: Aluminum, brass, steel, stainless steel, and cast iron all use different cutting speed ranges.
  • Tool material: Carbide tools usually tolerate higher cutting speeds than HSS tools.
  • Diameter matters: Larger tools need lower RPM to maintain the same surface speed at the cutting edge.

Frequently Asked Questions

Common questions about the Cutting Speed to rpm Converter

Angular velocity measures how fast something rotates, expressed as angle change per unit time. Common units include radians per second (rad/s), degrees per second, and revolutions per minute (RPM).
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Sources & References

International System of Units (SI): angular velocity

Angular velocity is measured in the radian per second (rad/s). Conversions between SI and other units use exact, internationally agreed factors maintained by NIST.
→Source: NIST — International System of Units (SI)

International System of Units (SI)

Authoritative definitions for angular velocity, from the BIPM SI Brochure (9th edition), the defining reference for the SI.
→Source: BIPM — SI Brochure (9th ed.)

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