SFM stands for Surface Feet per Minute — the speed at which the cutting edge of a tool (or the surface of a workpiece) moves past the cutting point. It is the imperial unit of cutting speed; the metric equivalent is meters per minute (m/min).

How do I calculate feed rate from RPM?

Feed rate (IPM) = RPM × chip load per tooth × number of flutes. In metric, feed rate (mm/min) = RPM × feed per tooth (mm) × number of flutes.

Is this surface feet per minute calculator free?

Yes. This SFM, RPM, feed rate and chip load calculator is completely free, runs in your browser, and requires no sign-up.

SFM to RPM Calculator

Convert surface speed (SFM or m/min) and tool diameter into spindle RPM in one click — then get feed rate and chip load for milling, turning, and drilling. Works in both imperial and metric.

Cutting speed (SFM)

Tool / part diameter (inch)

RPM —

How the SFM ↔ RPM conversion works

Cutting speed describes how fast the cutting edge travels past the material, while RPM is how fast the spindle turns. They are linked by the tool (or part) diameter:

Imperial: RPM = (12 × SFM) / (π × D) ≈ 3.82 × SFM / D (D in inches)
Imperial: SFM = (π × D × RPM) / 12 ≈ 0.262 × D × RPM
Metric: RPM = (1000 × V_c) / (π × D) (V_c in m/min, D in mm)
Metric: V_c = (π × D × RPM) / 1000

Feed rate & chip load

Once you know RPM, feed rate follows from how much each tooth removes per revolution (the chip load):

Feed rate: IPM = RPM × chip load (IPT) × number of flutes
Metric: mm/min = RPM × feed per tooth (mm) × number of flutes
Chip load: per tooth = feed rate ÷ (RPM × number of flutes)

Recommended starting SFM by material

General starting points for HSS and carbide tooling. Always defer to your tool manufacturer's data and adjust for rigidity, coolant, and finish.

Material	HSS (SFM)	Carbide (SFM)
Aluminum	250–300	600–1200
Brass	150–250	400–700
Mild steel (1018)	80–110	300–500
Alloy steel (4140)	50–80	200–350
Stainless (304)	40–70	150–300
Cast iron	50–80	200–400
Titanium	30–50	100–200

Frequently asked questions

What is the formula to convert SFM to RPM?

RPM = (12 × SFM) / (π × D), where D is the diameter in inches. The shortcut RPM ≈ 3.82 × SFM / D gives the same result. In metric, RPM = (1000 × V_c) / (π × D).

What does SFM (surface feet per minute) mean?

SFM is the imperial unit of cutting speed — the distance the cutting edge travels past the workpiece each minute. The metric equivalent is meters per minute (m/min), sometimes written V_c.

How do I work out feed rate from RPM?

Feed rate (IPM) = RPM × chip load per tooth × number of flutes. Switch the unit toggle to metric for mm/min.

Does this work for drilling and turning too?

Yes. For drilling, use the drill diameter; for turning, use the part diameter. The SFM-to-RPM relationship is the same — only the diameter you enter changes.