SFM to RPM Calculator
Convert SFM to RPM or RPM to SFM. Switch to metric for Vc in meters per minute and diameter in millimeters.
Formula and worked example
Metric: RPM = (Vc × 1,000) ÷ (π × diameter mm)
Frequently asked questions
How do I convert SFM to RPM?
Multiply SFM by 12, then divide by pi times diameter in inches. A smaller cutter needs more RPM to reach the same surface speed. Always compare the result with the machine’s spindle limit and the tool manufacturer’s recommended cutting-speed range.
How do I convert RPM back to SFM?
Multiply RPM by diameter in inches and pi, then divide by 12. This reverse calculation is useful when the spindle has a fixed speed or maximum RPM and you need to know the surface speed the tool or workpiece will actually see.
What is Vc, and how is it different from SFM?
Vc is the metric cutting speed, normally expressed in meters per minute. SFM expresses the same surface-speed concept in feet per minute. For metric calculations, RPM equals Vc times 1,000 divided by pi times diameter in millimeters.
More machining calculators
30+ machinist calculators in your pocket.
Need tap drill, thread wire, bolt circle? ShopCalc has 30+ machinist calculators offline.
