Feed per Tooth Calculator
Feed per tooth (fz, also written IPT for inches per tooth or mm/tooth in metric) is the chip thickness each flute of an end mill removes in one revolution. It is the single most important parameter for tool life, surface finish, and cycle time in milling. Run it too high and the tool fractures; too low and the tool rubs and burns. This feed per tooth calculator solves fz from feed rate and RPM, converts feed per tooth to mm/min feed rate for metric CNC, or recommends a baseline fz for your material.
The feed per tooth formula
Feed per tooth (fz or IPT) is the chip load equation turned inside out:
- fz = Feed rate / (RPM x flutes)
- Equivalent: Feed rate = RPM x fz x flutes
Example: a 4-flute end mill running 3,000 RPM at 24 IPM has fz = 24 / (3000 x 4) = 0.002 IPT. In metric: 24 IPM x 25.4 = 610 mm/min, and fz = 0.051 mm/tooth. That matches a standard chip load for mild steel on a half inch end mill.
Feed per tooth to mm/min
A feed per tooth to mm min calculator takes fz (mm/tooth) and returns feed rate in millimeters per minute. The formula is mm/min = RPM x fz x flutes. For a 3-flute end mill at 8,000 RPM with fz = 0.1 mm/tooth: mm/min = 8000 x 0.1 x 3 = 2,400 mm/min. That is the F value the control sees.
Feed per tooth baselines
| Material | fz baseline (IPT) | fz baseline (mm/tooth) |
|---|---|---|
| Aluminum 6061 | 0.004 | 0.102 |
| Mild steel 1018 | 0.002 | 0.051 |
| Alloy steel 4140 | 0.0015 | 0.038 |
| Stainless 304/316 | 0.0015 | 0.038 |
| Tool steel (A2, D2) | 0.001 | 0.025 |
| Cast iron | 0.003 | 0.076 |
| Brass | 0.003 | 0.076 |
| Titanium Ti-6Al-4V | 0.001 | 0.025 |
| Inconel 718 | 0.0008 | 0.020 |
| Plastic (Delrin) | 0.005 | 0.127 |
These are baselines for a 0.5 inch (12.7 mm) end mill. Scale 0.5x for 1/8 inch tools and 1.25x for 3/4 inch tools.
Feed per tooth calculator metric
A feed per tooth calculator metric workflow accepts both fz in mm/tooth and feed rate in mm/min. The conversion is mm/tooth = IPT x 25.4. So 0.002 IPT = 0.051 mm/tooth; 0.004 IPT = 0.102 mm/tooth. This calculator returns both units simultaneously so metric CNC programmers (Fusion 360, SolidCAM, HyperMill) can pull the value without an extra conversion step.
How to use fz in your CAM
Every modern CAM system (Fusion 360, Mastercam, HyperMill, SolidCAM, Edgecam) accepts fz in either IPT or mm/tooth and computes feed rate automatically from spindle RPM and flute count. Start at the baseline fz for your material, set an appropriate cutting speed (SFM), then let the CAM compute F. First-cut safety: program F at 80 percent of the value; listen and look at chips before dialing up.