Feed Rate Calculator
Cutting Speed Tells the Spindle How Fast, Feed Rate Tells It How Far
RPM alone doesn't determine how quickly a cutter moves through material — feed rate does, and it's calculated differently depending on the operation. A milling cutter with multiple teeth accumulates feed per tooth across every flute on every revolution, while a single-point turning or drilling tool advances once per revolution. Mixing up the two formulas produces a feed rate that's off by a wide margin.
The Formulas
Milling: Feed Rate = RPM × Number of Teeth × Chip Load
Turning / Drilling: Feed Rate = RPM × Feed per Revolution
Turning / Drilling: Feed Rate = RPM × Feed per Revolution
Worked Examples
| Operation | Inputs | Feed Rate |
|---|---|---|
| Milling | 3,000 RPM, 4 flutes, 0.002 in/tooth chip load | 24.0 in/min |
| Turning / Drilling | 1,200 RPM, 0.008 in/rev feed | 9.6 in/min |
In the milling formula, each additional flute on a cutter increases feed rate proportionally at the same chip load — a 4-flute end mill can run twice the feed rate of an otherwise identical 2-flute tool without changing chip load per tooth.
Where This Calculation Matters
- CNC program setup — converting a tool manufacturer's recommended chip load or feed-per-revolution into an actual feed rate for the machine controller.
- Tool life and surface finish — feed rate that's too aggressive for a given chip load risks tool breakage or poor finish; too conservative wastes cycle time.
- Tool changeover — recalculating feed rate whenever flute count, chip load recommendation, or RPM changes with a new tool or material.
How to Use This Calculator
- Choose the mode: Milling or Turning / Drilling.
- For milling, enter Spindle Speed (RPM), Number of Teeth/Flutes, and Chip Load (in/tooth).
- For turning or drilling, enter Spindle Speed (RPM) and Feed per Revolution (in).
- Select Calculate to get the feed rate in inches per minute.
Related Calculations
Determine spindle RPM first from the material's cutting speed with the Metal Cutting Speed Calculator.