Spindle Speed & Feed Calculator

Calculate RPM, feed rate, chip load, and cut time for milling and turning operations. Perfect for machinists, CNC operators, and DIY enthusiasts.

mm
m/min
mm/tooth
mm
0 RPM
Spindle Speed 0
Feed Rate 0 mm/min
Chip Load 0 mm³/min
Cut Time –

Test Cases

Metric Example

D=20 mm, V=40 m/min, Z=1, Ft=0.01 mm

Expected: RPM ≈ 636.62, FeedRate ≈ 6.37 mm/min

Imperial Example

D=0.75 in, SFM=300, Z=2, IPT=0.002 in

Expected: RPM ≈ 1528, FeedRate ≈ 6.11 IPM

How It Works

Spindle Speed (RPM) Formulas

RPM = (1000 × V) / (π × D) Where: V = Cutting Speed (m/min) D = Diameter (mm) π ≈ 3.14159
RPM = (SFM × 3.82) / D Where: SFM = Surface Feet per Minute D = Diameter (inches) 3.82 ≈ 12/π

Feed Rate Formulas

Feed Rate (mm/min) = RPM × Ft × Z Where: Ft = Feed per Tooth (mm) Z = Number of Teeth
Feed Rate (IPM) = RPM × IPT × Z Where: IPT = Inches per Tooth Z = Number of Teeth

Cut Time Formula

Cut Time (min) = Cut Length / Feed Rate Note: Units must match (mm with mm/min, inches with IPM)

Worked Example (Metric)

For a 10mm end mill cutting aluminum at 200 m/min, with 2 teeth and 0.1 mm feed per tooth:

RPM = (1000 × 200) / (π × 10) ≈ 6366 Feed Rate = 6366 × 0.1 × 2 = 1273.2 mm/min

FAQ

What are typical cutting speeds for common materials? +

Steel: 30-60 m/min (100-200 SFM) for HSS, 60-120 m/min (200-400 SFM) for carbide

Aluminum: 150-300 m/min (500-1000 SFM)

Wood: 300-600 m/min (1000-2000 SFM)

Plastics: 50-150 m/min (150-500 SFM)

How do I measure tool diameter accurately? +

Use a micrometer for precise measurement. For end mills, measure the cutting diameter, not the shank. For drills, measure across the cutting lips.

Why is my calculated RPM different from my machine’s actual RPM? +

Machine RPM can vary due to load, tool condition, material variations, and machine calibration. Always start with conservative settings and adjust based on actual performance.

How do I convert between metric and imperial units? +

1 inch = 25.4 mm, 1 m/min = 3.28084 SFM. This calculator automatically converts values when you switch between unit systems.

Pro Tips

  • Start with conservative speeds and feeds, then gradually increase while monitoring tool performance.
  • For carbide tools, you can typically use higher speeds than with HSS tools.
  • Use coolant or lubricant for metals to extend tool life and improve surface finish.
  • Consider chip evacuation – proper feeds help create chips that carry heat away from the cut.
  • Always consult your tool manufacturer’s recommendations for optimal performance.