Drill Feed Rate Calculator
A drill feed rate calculator turns spindle RPM and feed per revolution into the feed rate you program on a mill, lathe, or drill press. Feed per revolution scales with drill diameter in a predictable way (typically 0.015 IPR per inch of drill in steel), and the calculator applies that scaling automatically. Output is given in IPR, IPM, and mm/min so the same numbers work on any CNC control.
Drill feed rate formula
- Feed rate (IPM) = RPM x IPR where IPR is the feed per revolution.
- IPR scales with drill diameter: typical values are 0.018 IPR per inch of diameter in mild steel, 0.020 in aluminum, 0.012 in stainless, 0.010 in titanium.
- RPM = (SFM x 12) / (pi x D) in compute mode, where D is drill diameter in inches and SFM is the target cutting speed.
For a 1/4 inch HSS drill in mild steel: SFM = 80, so RPM = (80 x 12) / (pi x 0.25) = 1,222 RPM. IPR = 0.018 x 0.25 = 0.0045. Feed rate = 1,222 x 0.0045 = 5.5 IPM. Convert to metric: 5.5 x 25.4 = 139.7 mm/min.
Drill feed per revolution (IPR) reference
Feed per revolution in a drill scales roughly linearly with diameter. These values are IPR per inch of drill diameter.
| Material | IPR per inch of drill D | Example (1/4" drill) |
|---|---|---|
| Aluminum | 0.020 | 0.0050 |
| Mild steel (1018) | 0.018 | 0.0045 |
| Alloy steel (4140) | 0.014 | 0.0035 |
| Stainless steel | 0.012 | 0.0030 |
| Cast iron | 0.020 | 0.0050 |
| Titanium | 0.010 | 0.0025 |
| Plastic | 0.025 | 0.0063 |
Drill feed rate vs milling feed rate
Milling feed is chip-load-per-tooth times flutes times RPM. Drilling feed is feed-per-revolution times RPM, with no flute multiplier because the two cutting lips of a drill share one chip per revolution. That is why a drill feed rate calculator and a mill feed rate calculator produce different IPM for the same SFM: a 1/4 inch HSS drill at 1,222 RPM and 0.0045 IPR feeds at 5.5 IPM, while a 1/4 inch HSS end mill at 1,222 RPM and 0.002 IPT chip load with 4 flutes feeds at 9.8 IPM.
Adjusting feed for hole depth
For shallow holes (up to about 3x drill diameter) use the full calculated feed. For deep holes over 5x diameter, drop feed 20-30 percent because the chip has further to travel out of the flutes. Add pecks at about 1x diameter intervals to break the chip and clear it from the hole. For blind holes, add a 0.5-1.0 second dwell at depth before the retract to clean up the bottom.
Feed rate overrides
Use the override field to enter a specific IPR (for example, from a tooling vendor's data sheet). A few common cases where the table default is wrong: spade drills (lower IPR than twist drills), step drills (use the largest step diameter), carbide tipped drills in hard materials (specific IPR from the manufacturer), and gun drills (very low IPR with high pressure coolant).