SFM to RPM Calculator
Convert surface speed to spindle speed. Enter the tool diameter and the recommended surface feet per minute to get the matching RPM.
SFM to RPM calculator
Spindle speed
- RPM
RPM = (SFM x 12) / (pi x diameter in inches)
RPM = (m/min x 1000) / (pi x diameter in mm)
Editorial estimate only
These are conservative starting points, not a guarantee. Verify against manufacturer tooling data and your machine manual. Confirm spindle power, workholding and coolant before cutting.
What is surface speed?
Surface speed (SFM in imperial, m/min in metric) is how fast the cutting edge moves past the material. Every material has a recommended surface speed window. Spindle speed (RPM) is the rotation rate that produces that surface speed for a given cutter diameter. Smaller cutters spin faster to reach the same surface speed.