Cutting Speed Calculator
RPM from surface speed and tool diameter
📚 Learn more — how it works, FAQ & guide Click to expand
Learn more — how it works, FAQ & guide
Click to expand
Cutting speed calculator (SFM → RPM)
Calculate optimal spindle RPM for any material + tool combination.
How to use this tool
- 1
Pick material + operation
Determines target surface speed (SFM).
- 2
Enter tool diameter
Drill bit, end mill, or workpiece OD.
- 3
See RPM
Optimal spindle speed for clean cuts.
Frequently Asked Questions
RPM formula
RPM = (SFM × 12) / (π × D), where SFM = surface feet per minute, D = tool diameter in inches. Metric: RPM = (Vc × 1000) / (π × D_mm).
Why SFM matters
Every material has optimal cutting speed. Too fast burns tools. Too slow causes work hardening. Target SFM = best balance.
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100% Privacy. This tool runs entirely in your browser. Your data is never uploaded to any server.