Calculate RPM, IPM, SFM, IPT and more.

Below are variable abbreviations and formulas for many common milling operations.

Click here to download a printable PDF file containing these formulas.

Looking for speed & feed calculators and recommendations for your Dapra tooling? Click here for our extensive library of free resources, or contact an applications specialist to discuss the optimal parameters for your milling program.

Variables / Abbreviations

  • Speed – Surface Feet per Minute (SFM)
  • Feed – Inches per Minute (IPM)
  • Feed per Tooth (FPT)
  • Adjusted Feed per Tooth – Chip Thinning (AFPT)
  • Feed per Revolution (FPR)
  • Depth of Cut (DOC)
  • Width of Cut (WOC)
  • Tool Diameter (D)
  • # of Teeth in Cutter (Z)
  • Metal Removal Rate – Cubic Inches per Minute (MRR)


Milling Formulas

  • Speed (RPM) = (SFM x 3.82) / D
  • Feed (IPM) = RPM x FPT x Z
  • SFM (Surface Feet per Minute) = (RPM x D) / 3.82
  • IPT (Inches per Tooth) = (IPM / RPM) / Z
  • MRR (Cubic Inches per Minute) = IPM * WOC * DOC
  • AFPT (@ less than 1/2 dia. WOC) = IPM x sqroot of (D / WOC)
  • HP (Horsepower Consumption) = MRR x mf
    • mf - steel = 1
    • mf - gray iron = .65
    • mf - aluminum = .3
    • * - 1.5% from total for every degree positive


For lead angle (chip thinning) and effective cutting diameter compensation, see corresponding tool reference page / catalog.


Radial Engagement Feed Adjustment Chart

Click here to download a printable PDF file of this chart.

Radial Engagement Feed Adjustment Chart


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