Surface Feet per Minute (SFM) Calculator
SI
Imp
Imperial
Inputs
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Diameter
(D)
Tool diameter (milling/drilling) or workpiece diameter (turning).
in
Cutting speed
(Vc)
Surface cutting speed. Look up a starting value for your material below.
SFM
Results
Default result
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Spindle speed
(n)
382
rpm
Method notes
3 notes
RPM = cutting speed ÷ (π × diameter). In imperial: RPM = (SFM × 12) ÷ (π × diameter in inches) ≈ 3.82 × SFM / D.
For milling and drilling the diameter is the tool diameter; for turning it is the work diameter.
Cutting speeds in the table are starting points — tune for depth of cut, feed, coating and rigidity.
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