Metric
RPM = (1000 × Vc) ÷ (π × D)
Vc = (π × D × RPM) ÷ 1000
Vc: m/min · D: mm
CNC machining calculator
CNC Feeds and Speeds Calculator
Calculate theoretical spindle speed and feed from cutting values you provide for milling, turning, or drilling. This tool does not recommend material cutting data.
Calculation reference
Formulas Used
Enter cutting conditions from the tool manufacturer, process plan, or another source you trust. Results are arithmetic conversions, not a safe-parameter recommendation.
Imperial
RPM = (12 × SFM) ÷ (π × D)
SFM = (π × D × RPM) ÷ 12
SFM: ft/min · D: inch
Milling feed
Feed rate = RPM × Z × fz
Z is the number of cutting teeth used for the calculation. fz is feed per tooth.
Turning and drilling feed
Feed rate = RPM × fn
fn is feed per revolution. Feed rate is mm/min or in/min.
For milling and drilling, D is the relevant cutting tool diameter. For turning, D is the workpiece diameter at the cutting position. This calculator does not apply machine spindle limits, effective cutter-diameter corrections, tooth engagement factors, or material-specific recommendations.
Using the calculator
How to Use
- Select Milling, Turning, or Drilling, then choose Metric or Imperial units.
- Enter the relevant diameter and a cutting speed from your chosen source.
- For milling, enter the tooth count and feed per tooth. For turning or drilling, enter feed per revolution.
- Review the calculated RPM and feed against your machine, tool documentation, workholding, and setup.
Input definitions
Milling, Turning, and Drilling
Milling
Table feed uses spindle RPM, the entered tooth count, and feed per tooth. Confirm whether the entered tooth count reflects the teeth engaged for your calculation.
Turning
Feed rate uses RPM and feed per revolution. Enter the workpiece diameter at the cutting position, not an insert or holder dimension.
Drilling
Feed rate uses RPM and feed per revolution. Enter the drill cutting diameter and check the drill manufacturer’s guidance for the applicable conditions.
Technical references
Formula Sources
These sources describe formula relationships. No material speed or feed presets are included.
- Sandvik Coromant: Milling formulas and definitions
Spindle speed, cutting speed, feed per tooth and table feed formulas.
- Sandvik Coromant: Turning formulas, metric
Metric spindle speed, cutting speed, workpiece diameter and feed-per-revolution relationships.
- Haas Tooling: Drilling speeds and feeds
Drilling RPM, cutting speed, tool diameter, feed per revolution and feed rate formulas.
Common questions
FAQ
What is the difference between RPM and cutting speed?
RPM is spindle revolutions per minute. Cutting speed describes the surface speed at the cutting diameter; their relationship depends on diameter and the selected unit system.
How are feed per tooth and feed per revolution different?
Feed per tooth is a milling input multiplied by tooth count and RPM. Feed per revolution is used for turning or drilling and multiplied by RPM.
Does the calculator provide recommended cutting data?
No. Provide cutting values from an applicable tool source or process plan. Confirm them for the material, tool, machine, and setup before machining.
Why can actual feed differ from the result?
Machine limits, engagement, interpolation, control settings, and process-specific corrections can affect programmed or achieved values.