# SFM to RPM: Calculator, formulas, and Charts

The cutting tools catalogs or our experience tells us the SFM (Cutting Speed) we need to use for a given application. On the other hand, the CNC machine is programmed with the RPM (Spindle speed). Therefore it is common that we need to compute the RPM from a given SFM either for programming or to ensure that the SFM we want to run at is within the machineâ€™s limit. It is calculated by dividing the cutting speed by the cutterâ€™s circumference.

## SFM to RPM Formula

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

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

## SFM to RPM Calculator

The cutting tools catalogs or our experience tells us the SFM (Cutting Speed) we need to use for a given application. On the other hand, the CNC machine is programmed with the RPM (Spindle speed). Therefore it is common that we need to compute the RPM from a given SFM either for programming or to ensure that the SFM we want to run at is within the machineâ€™s limit. It is calculated by dividing the cutting speed by the cutterâ€™s circumference.