# RPM to SFM: Calculator, formulas, and Charts

CNC machines are programmed by the spindle speed (RPM), but cutting data is typically given in SFM. Therefore it is common that we need to compute the SFM from a given RPM to determine the cutting speed at which our cutting tool is working. It is calculated by dividing the cutterâ€™s circumference by the cutting speed.

## RPM to SFM Formula

• d â€“ [Inch] (Diameter)
• n â€“ [RPM] (Revolutions per minute)
• Vc â€“ [SFM] (Surface feet per minute)

$$\large SFM = \huge \frac{n \times \pi \times d}{12}$$

## RPM to SFM Calculator

CNC machines are programmed by the spindle speed (RPM), but cutting data is typically given in SFM. Therefore it is common that we need to compute the SFM from a given RPM to determine the cutting speed at which our cutting tool is working. It is calculated by dividing the cutterâ€™s circumference by the cutting speed.

## RPM to RPM Chart (Inch)

Find out the SFM according to your toolâ€™s diameter and the machineâ€™s RPM

## RPM to SFM Chart (Metric)

Find out the SFM according to your toolâ€™s diameter and the machines RPM

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