Machining Calculator for Speeds, Feeds, and Spindle RPM
Size milling, drilling, and turning speeds and feeds. RPM = SFM × 3.82 / D from diameter and material. A 0.5 in mill in aluminum at 800 SFM starts near 6112 RPM.
What is a machining calculator?
A machining calculator on this site answers one cutting question: what spindle speed and feed to try for a given tool diameter and material. The inch shortcut is RPM = SFM × 3.82 / D. Milling then multiplies RPM by chip load and flute count. Drilling and turning multiply RPM by feed per revolution.
- Use it for CNC or manual mill, drill, and lathe starting speeds.
- Do not use it to look up tap drill diameters or thread percentages.
- Do not treat the SFM table as a toolmaker maximum.
Core tools
Speeds and Feeds Calculator
Enter diameter, material, and chip load to get milling, drilling, or turning RPM and feed from the SFM formula.
Machining Time Calculator
Cutting time per pass and total from cut length, feed rate, passes, and approach — the floor of cycle time.
Tapping Torque Calculator
Tap drill size and tapping RPM from thread size and material, with torque reference bands by workpiece class.
Tool Life Calculator
Taylor equation tool life in minutes from surface speed, exponent, and constant — plan changes before the edge dies.
Start here
Most visits are for a milling or drilling RPM, not a separate lathe site. Open the speeds and feeds calculator, leave milling selected for an end mill, or switch to drilling for a twist drill. After you have RPM, use the motor torque calculator if the question becomes whether the spindle can hold that speed.
Workflow
- Set milling RPM and chip load on the speeds and feeds calculator.
- Switch the same page to drilling when the job is a twist drill: drilling speeds and feeds.
- Check shaft torque at that RPM with the motor torque calculator.
Use cases
- CNC end mill in aluminum: 0.5 in carbide, 4 flutes, 800 SFM starts near 6112 RPM and 97.8 IPM. Calculate milling feed.
- Manual twist drill in mild steel: HSS drilling uses a lower surface speed than carbide milling. Calculate drill RPM.
- Lathe facing or OD turn: turning stays on the same calculator and uses feed per revolution. Calculate turning speed.
Which tool for which job
| Goal | Open |
|---|---|
| Milling RPM and IPM | Speeds and feeds, milling |
| Drill RPM and feed per rev | Speeds and feeds, drilling |
| Turning RPM and feed per rev | Speeds and feeds, turning |
| Torque at the spindle RPM | Motor torque calculator |
FAQ
What is a machining calculator on this hub?
It is the entry for shop speeds and feeds. The interactive page calculates spindle RPM and feed for milling, drilling, or turning from diameter, material, and chip load.
How do I calculate speeds and feeds?
Open the speeds and feeds calculator, enter tool diameter and material, and read RPM. Inch form: RPM = SFM × 3.82 / D. Mill feed is RPM × chip load × flutes.
What is the difference between this hub and a drill size chart?
This hub calculates cutting RPM and feed. A drill and tap chart lists hole diameters for thread sizes. Those are different jobs, and this hub does not publish a tap drill table.