Feeds and Speeds Calculator
A feeds and speeds calculator turns a target surface cutting speed and chip load into the two machine inputs you actually program: spindle RPM and feed rate. This calculator handles milling (end mill or face mill), drilling, and turning on a lathe, and works for any tool material (HSS or carbide) and a broad library of workpiece materials including aluminum, mild steel, stainless, titanium, and plastic.
The core feeds and speeds formulas
Every feeds and speeds calculator reduces to two equations from the Machinery's Handbook:
- RPM = (SFM x 12) / (pi x D) where SFM is surface feet per minute and D is the tool or workpiece diameter in inches.
- Feed rate (IPM) = RPM x chip load x number of flutes for milling.
For drilling, feed rate is specified in inches per revolution (IPR) instead of per tooth, so the equation is feed rate = RPM x feed_per_rev. For turning on a lathe, feed is also IPR and the diameter in the RPM equation is the workpiece diameter being cut, not the tool.
Typical cutting speeds (SFM) by material
| Material | HSS SFM | Carbide SFM |
|---|---|---|
| Aluminum | 600 | 1500 |
| Mild steel | 100 | 350 |
| Alloy steel (4140) | 70 | 250 |
| Stainless steel | 60 | 200 |
| Cast iron | 80 | 250 |
| Brass | 250 | 500 |
| Titanium | 40 | 120 |
| Plastic (Delrin) | 800 | 2000 |
Using this speeds and feeds calculator
Pick an operation (mill, drill, turn), enter your tool or workpiece diameter, select the material and tool material, and the calculator returns spindle RPM, feed rate, chip load per tooth, and an approximate metal removal rate. Inputs accept both imperial (inches) and metric (mm), so a feeds and speeds calculator metric setup is a single unit toggle away. Haas, Mazak, Okuma, and Tormach control macros all accept the same RPM and IPM values this calculator produces.
Drilling and turning
A drilling feeds and speeds calculator uses a feed per revolution scaled to drill diameter: typical values run 0.001 IPR for a 1/16 drill up to 0.015 IPR for a 3/4 drill in mild steel. For turning, feed per revolution of 0.005-0.010 IPR is normal for finishing, 0.015-0.020 IPR for roughing. The calculator falls back to these ranges automatically when you do not specify a chip load.