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Cutting Speed Calculator

Calculate surface cutting speed (Vc) from tool diameter and spindle RPM for turning and milling.

Cutting speed
157.1 m/min
Vc = π · D · N / 1000. Higher surface speed removes material faster but shortens tool life.
In m/min
157.1 m/min
In ft/min (SFM)
515.4 ft/min

How it works

  1. 1Enter the tool or workpiece diameter in mm or inches.
  2. 2Enter the spindle speed in RPM.
  3. 3The calculator applies Vc = π·D·N/1000 and shows the result in m/min and ft/min (SFM).

Use cases

  • Setting the spindle speed when programming a CNC turning or milling operation.
  • Verifying that an RPM keeps surface speed within the tool maker’s recommended Vc range.
  • Converting between metric m/min and imperial SFM for tooling data sheets.

Frequently asked questions

What is cutting speed and why does it matter?

Cutting speed (Vc) is the speed the tool edge moves across the surface, in m/min or ft/min (SFM). Too low wastes time; too high causes rapid tool wear. Typical: 80–250 m/min for steel, 200–600 for aluminium.

How is cutting speed calculated?

Vc = π · D · N / 1000, with D in mm and N in rpm. A 50 mm tool at 1000 rpm gives Vc ≈ 157 m/min (about 515 SFM).

How do I get RPM from a recommended cutting speed?

Rearrange to N = 1000·Vc / (π·D). For 200 m/min on a 50 mm cutter, N ≈ 1273 rpm. Start at the low end of the range and adjust by chip colour and tool condition.

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