Lathe & mill
Spindle speed calculator
Turn a cutting speed into RPM for any cutter or part diameter. Add your machine's max RPM to see how hard you're pushing the spindle.
Spindle speed
—RPM
From your tooling data for this material
Cutter Ø on a mill, part Ø on a lathe
Shows spindle load and caps the result
Show the math
RPM = cutting speed × 12 ÷ (π × diameter)
Enter a cutting speed and diameter to see it worked out.