Feed Rate Calculator
Enter RPM, chip load and flutes to get feed in mm/min and IPM — the second number of every speeds-and-feeds pair.
Last updated: 2026-09-28
How the calculation works
- Each flute cuts once per revolution: feed per minute is chip load × flutes × RPM.
- Mils input serves US chip-load conventions (0.002 in = 0.0508 mm).
- The chip-load row converts back to mils for cross-checking imperial recommendations.
Formula
F = n × fz × z
| Symbol | Meaning | Unit |
|---|---|---|
F | Table feed | mm/min |
fz | Feed per tooth (chip load) | mm |
z | Number of flutes | — |
Worked example
Interpreting the result
Chip load is the physical contract: every tooth must take a real chip or it rubs, work-hardens and heats instead of cutting. Too much feed chips the edge or breaks the tool; too little is the more common hobbyist error — squealing, glazing and premature dulling. Adjust down for deep engagement, thin walls and long overhangs; increase (within reason) when the cut sounds clean and chips are the right color.
Assumptions
- Full slotting convention for starting values; radial engagement modifies effective chip load.
- Sharp, healthy tooling — worn tools need feed reductions.
Limitations
- Does not compute radial chip thinning compensation (relevant at low stepover in finishing).
- Drilling uses per-revolution feed, not per-tooth — different model.
Frequently asked questions
How do I calculate feed rate for milling?
Feed = RPM × chip load × flutes. 10,000 RPM, 4 flutes, 0.03 mm: 1200 mm/min (47 IPM).
What happens if my feed is too slow?
The tool rubs instead of cutting: heat goes into the tool instead of the chip, work-hardening the surface and dulling the edge prematurely. Squealing and glazing are the audible symptoms.