Feeds & Speeds Calculator
Spindle RPM and feed rate for milling — metric and imperial, free.
Enter tool diameter, number of flutes, chip load and cutting speed. The calculator returns the spindle RPM (n = Vc × 1000 / π × D) and the feed rate (f = RPM × flutes × chip load) — the two numbers every CNC and router job starts from.
FAQ
What is chip load?
Chip load is the thickness of material each flute removes per revolution. Too low and the tool rubs and heats up; too high and the cutter or spindle overloads. Tool manufacturers publish recommended chip load ranges per material.
Where do I get the cutting speed?
Cutting speed (Vc in m/min, or SFM in inches) depends on the tool coating and material: as starting points, ~100 m/min carbide in aluminium, ~50 in mild steel, ~200+ in wood and plastics with router bits. Adjust from the tool datasheet.
Should I run exactly the calculated RPM?
Round to the nearest speed your machine offers and listen to the cut. The formula gives a mathematically correct starting point; rigidity, coolant and fixturing shift the practical optimum.
What is the difference between cutting speed and feed rate?
Cutting speed (Vc) is how fast the tool edge moves across the material surface, in metres per minute - it is set by spindle RPM and tool diameter. Feed rate is how fast the whole tool advances through the workpiece, in mm/min - in Spanish, velocidad de avance. They are linked but independent: for a 10 mm tool at 100 m/min you need about 3,180 RPM, and the feed is then that RPM times chip load times the number of flutes. Both belong in the same calculation, which is what this tool does.