Surface Feet Per Minute (SFM) Calculator

CORE CNC

Find cutting speed (surface feet per minute) from tool diameter and spindle RPM, the core number every speeds-and-feeds calculation starts from.

—
Surface Feet per Minute (SFM)
—
Meters per Minute (m/min)

Formula: SFM = (pi times D times RPM) divided by 12, with D in inches. m/min = SFM times 0.3048.

How it works

Surface speed is how fast a point on the cutting edge moves through the material, depending on diameter and RPM, not feed. Look up the recommended SFM for the tool and material combo, then use the Spindle RPM Calculator to convert it to a spindle speed.

FAQ

Does SFM change with depth of cut? No, SFM only depends on diameter and RPM. Depth of cut affects load, not surface speed.

What SFM should I run? It depends on tool material and workpiece material; carbide generally runs much higher SFM than HSS. Check the tool manufacturer chart.

Related Guides

CNC Calculators · Spindle RPM Calculator · Feed Rate Calculator

Spotted an error or have a suggestion for this calculator? Let us know →
Scroll to Top

The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.