1) Click Reset 
2) Enter all but one value 
3) Click Compute

Calculate Surface Feet Per Minute;
SFM = (Pi * Dia * RPM) / 12 
SFM = Surface Feet Per Minute 
Dia = Diameter (inches) 
RPM = Revs Per Minute 

Convert Between Inches & Millimeters 
.03936" = 1mm     25.4mm = 1"

Convert From Fraction to Decimal 
(Does not go from decimal to fraction)

© The Machinists' Exchange On-line. 
Used with permission.