Speeds and Feeds Calculator
Calculate milling and drilling RPM and feed from diameter, material, and chip load. Turning uses the same page.
Calculator
About this calculator
One speeds and feeds calculator for milling, drilling, and turning RPM. Starting surface speeds are shop starting points, not a guaranteed cut. Browse the machining calculator hub.
Calculation Results
6112 RPM
Feed 97.8 IPM · 800 SFM · Milling
Formula: RPM = SFM × 12 / (π × D); Feed = RPM × chip load × flutes
How to use this result
Set the spindle to the RPM and the table or axis to the feed. The number is a starting estimate from the surface speed you entered. It is not a toolmaker limit, and it ignores stickout, slotting, coolant, and machine rigidity. If the cut chatters, lower speed or chip load before you change diameter.
Continue Your Calculation
After the cutting RPM, check whether the spindle motor can deliver torque at that speed.
Starting surface speed (SFM)
Workshop starting points for milling. Drilling on this page uses about 70% of the milling speed (60% for 304). Confirm with the toolmaker.
| Material | HSS SFM | Carbide SFM | Mill chip load (0.5 in class) |
|---|---|---|---|
| Aluminum 6061 | 300 | 800 | 0.004 in/tooth |
| Mild steel 1018 | 90 | 350 | 0.003 in/tooth |
| Stainless 304 | 50 | 180 | 0.002 in/tooth |
| Cast iron | 70 | 250 | 0.003 in/tooth |
| Brass | 200 | 500 | 0.004 in/tooth |
| Acrylic | 300 | 600 | 0.005 in/tooth |
Speeds and feeds formula
Inch RPM: RPM = SFM × 12 / (π × D) ≈ SFM × 3.82 / D, with D in inches.
Metric RPM: RPM = Vc × 1000 / (π × D), with Vc in m/min and D in mm.
Milling feed: IPM = RPM × chip load × flutes.
Drilling or turning feed: IPM = RPM × feed per revolution.
Example: 0.5 in, 4-flute carbide end mill, aluminum, 800 SFM, 0.004 in/tooth. RPM = 800 × 3.82 / 0.5 = 6112 RPM. Feed = 6112 × 0.004 × 4 = 97.8 IPM.
Next, check shaft torque at that RPM with the motor torque calculator. Hub: machining calculator.
Which mode to use
| Job | Mode on this page | Feed input |
|---|---|---|
| End mill, face mill | Milling | in/tooth × flutes |
| Twist drill | Drilling | in/rev |
| Lathe OD or facing | Turning | in/rev |
| Spindle motor at the calculated RPM | Motor torque calculator | Not a cutting feed |
Frequently Asked Questions
How do I calculate milling RPM from SFM?
Use RPM = SFM × 12 / (π × D), often written SFM × 3.82 / D with D in inches. A 0.5 in carbide end mill in aluminum at 800 SFM is 6112 RPM.
What is the difference between milling feed and drilling feed?
Milling feed is RPM × chip load × flutes. Drilling and turning use RPM × feed per revolution. Do not multiply a drill by flute count.
What SFM should I start with for aluminum and mild steel?
On this page, aluminum 6061 starts near 300 SFM HSS or 800 SFM carbide. Mild steel 1018 starts near 90 SFM HSS or 350 SFM carbide. Lower the speed for slotting, long stickout, or no coolant, then confirm with the toolmaker.
Does this replace a drill and tap chart?
No. This calculator returns spindle RPM and feed. It does not list tap drill diameters for thread sizes.
How do I use the RPM result with a spindle motor?
Open the motor torque calculator and enter that RPM with the motor power. Cutting speed is not the motor nameplate rating.