What this calculator does
The Cutting Speed & Feed Calculator converts the recommended cutting speed of a material–tool combination into the spindle speed your machine should run at, and then works out the feed rate. It covers the three basic machining operations: turning on a lathe, drilling, and milling with a multi-tooth cutter.
Tool suppliers publish cutting speeds (Vc) in m/min or surface feet per minute (SFM) for each material and tool material — for example, around 20–30 m/min for HSS in mild steel, 150–300 m/min for carbide inserts in steel, and much higher in aluminum. Enter the speed together with the diameter of the workpiece (turning) or the tool (drilling, milling), and the calculator gives you the RPM and the feed rate in metric or imperial units.
How to use the Cutting Speed & Feed Calculator
- Choose the operation: turning, drilling, or milling.
- Choose the unit system: metric (mm and m/min) or imperial (inch and SFM). All length and feed fields follow this choice.
- Enter the diameter: the workpiece diameter for turning, or the tool diameter for drilling and milling.
- Enter the cutting speed Vc recommended for your tool and material.
- Enter the feed: feed per revolution for turning and drilling (for example 0.2 mm/rev), or the number of flutes and feed per tooth for milling (for example 4 flutes at 0.05 mm/tooth).
- Click "Calculate" to see the spindle speed and the feed rate to dial into the machine.
Formulas
For drilling, the cutting speed is taken at the drill's outer diameter, which is standard practice. For turning, the diameter is that of the surface being machined; as the diameter changes during facing, the ideal RPM changes with it.
Examples
- Turning a 50 mm steel shaft with a carbide insert at Vc = 200 m/min: n = 200,000 ÷ (π × 50) ≈ 1,273 RPM. With a feed of 0.2 mm/rev, the feed rate is ≈ 255 mm/min.
- Drilling a 10 mm hole with an HSS drill at Vc = 30 m/min: n = 30,000 ÷ (π × 10) ≈ 955 RPM. With 0.15 mm/rev, the feed rate is ≈ 143 mm/min.
- Milling with a 1/2" four-flute end mill at Vc = 300 SFM and fz = 0.002 in/tooth: n = 300 × 12 ÷ (π × 0.5) ≈ 2,292 RPM, and the feed rate is 2,292 × 4 × 0.002 ≈ 18.3 in/min.
Frequently asked questions
What is cutting speed?
It is the speed of the material surface relative to the cutting edge, measured along the circumference. It depends mainly on the workpiece material and the tool material, and it is the primary factor in tool life. Spindle RPM, by contrast, also depends on diameter.
Why does the machine's RPM differ from the result?
Machine spindles run in discrete gear steps and old lathes change RPM through pulleys, so you select the closest available speed. Choose the lower step when in doubt with fragile setups, and the higher step for better productivity.
What cutting speed should I use?
Use the value printed in your tool supplier's catalog for the specific material. As rough starting points: HSS in mild steel about 20–30 m/min, carbide turning inserts in steel 150–300 m/min, HSS in aluminum 100–300 m/min, and carbide in aluminum up to 500 m/min and more. Always reduce the speed for interrupted cuts and hard materials.
What is the difference between feed per tooth and feed per revolution?
Feed per revolution f is how far the tool advances during one full spindle revolution — the natural unit for single-point turning tools and drills. Feed per tooth fz is how much each cutting edge removes per pass; a milling cutter with z teeth advances z × fz per revolution, which is why the milling formula multiplies by the tooth count.
Can I mix metric and imperial fields?
No — pick one unit system and use it for diameter, cutting speed, and feed alike. The formulas are unit-consistent within each system, so results come out directly in mm/min or in/min.
Is my data saved or sent anywhere?
No. Every calculation runs in your browser, and nothing you type is stored or sent to a server.
Related calculators
Other free calculators commonly used with this tool: Bolt Torque Calculator, Gear Ratio Calculator, and Belt & Pulley Calculator.
Want a deeper walkthrough? Read our cutting speed and feed guide.