What is cutting speed in machining?

Cutting speed (v) is the speed at which the cutting edge of the tool moves relative to the workpiece surface, measured in m/min or ft/min. It is a key parameter for tool life and surface finish.

How do I calculate RPM from cutting speed?

Use n = 1000 × v / (π × D), where v is cutting speed in m/min and D is the tool or workpiece diameter in mm. This gives the required spindle speed in RPM.

What cutting speed should I use for steel?

For mild steel with HSS tools, typical cutting speed is 25–35 m/min. With carbide tools, it increases to 100–200 m/min. Always refer to your tool manufacturer's recommendations.

Does cutting speed change with tool diameter?

Cutting speed is independent of diameter—it's a material property. However, the RPM needed to achieve a given cutting speed changes inversely with diameter: larger tools need lower RPM.

What is the difference between cutting speed and feed rate?

Cutting speed (v) is the peripheral speed of the tool or workpiece. Feed rate (vf) is the linear advance of the tool per unit time. They are related but independent parameters in machining.

Free Engineering Tool #206

Cutting Speed ↔ RPM Calculator

Convert between cutting speed (v) and spindle RPM (n). Enter either value plus tool/workpiece diameter for bidirectional calculation.

v = πDn / 1000 Bidirectional Metric / Imperial

Results

Spindle RPM

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Cutting Speed

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Circumference

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Cutting Speed to RPM

The relationship between cutting speed and spindle RPM is:

v — cutting speed (m/min)
D — tool/workpiece diameter (mm)
n — spindle speed (RPM)

RPM to Cutting Speed

Recommended Cutting Speeds

Material	HSS (m/min)	Carbide (m/min)
Mild Steel	25–35	100–200
Stainless Steel	15–25	60–120
Cast Iron	20–40	80–160
Aluminium	60–100	200–500
Brass	50–80	150–300

Example — Carbide milling cutter Ø50 in steel

Given: v = 150 m/min, D = 50 mm

n = 1000 × 150 / (π × 50) = 150000 / 157.08 = 955 RPM

Cutting Speed ↔ RPM Calculator | Free Online Machining Tool

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Results

Cutting Speed to RPM

RPM to Cutting Speed

Recommended Cutting Speeds