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Cutting Speed & Machining Feed Rate Calculator (CNC / Milling / Lathe)

Machining speeds and feeds dictate tool life, surface finish, and cutting productivity in computer numerical control (CNC) milling and turning.

Recommended tool surface speed in m/min (Carbide on Al ≈ 250 - 500; Steel ≈ 80 - 180; Titanium ≈ 30 - 60).

Tool diameter in millimeters (or stock outer diameter for turning).

Number of cutting edges/flutes on the endmill.

Target chip thickness per flute in mm.

Axial engagement depth in mm.

Radial stepover engagement width in mm.

Calculated Result
3979 RPM

Target Spindle Speed

Spindle Speed

3979 RPM

Table Feed Rate (Vf)

954.9 mm/min

Feed Per Revolution (fn)

0.24 mm/rev

Surface Speed (SFPM)

492.1 ft/min

Material Removal Rate (MRR)

28.65 cm³/min

Calculation Breakdown

  1. 1. Spindle RPM CalculationRPM = (1000 · Vc) / (π · D) = (1000 · 150) / (π · 12) = 3979 RPM
  2. 2. Linear Feed Rate CalculationVf = RPM · fz · z = 3979 · 0.06 mm/tooth · 4 flutes = 954.9 mm/min
  3. 3. Chip Load VerificationFeed per rev fn = 0.06 · 4 = 0.24 mm/rev. Cut parameters ap = 5 mm, ae = 6 mm yield MRR = 28.65 cm³/min

Spindle RPM vs Tool Diameter (Vc = 150 m/min)

Interactive visualization based on your current inputs

RPM
0.02.0k4.0k6.0k8.0k6 mm8 mm10 mm12 mm16 mmDiameter (mm)RPM

What Is the Cutting Speed & Machining Feed Rate Calculator (CNC / Milling / Lathe)?

Speeds and feeds define the rotational tool velocity and linear workpiece traverse rate in subtractive CNC machining.

How Does the Cutting Speed & Machining Feed Rate Calculator (CNC / Milling / Lathe) Work?

Rotational speed matches tool peripheral linear speed to material shear limits; linear table feed ensures each cutting flute shears a uniform chip.

Cutting Speed & Machining Feed Rate Calculator (CNC / Milling / Lathe) Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

N = \frac{1000 \cdot V_c}{\pi \cdot D}, \quad V_f = N \cdot f_z \cdot z, \quad \text{MRR} = \frac{a_p \cdot a_e \cdot V_f}{1000}

Spindle RPM equals 1000 times cutting speed over pi times diameter. Feed rate is RPM times chip load times flute count.

How to Use the Cutting Speed & Machining Feed Rate Calculator (CNC / Milling / Lathe)

  1. Enter manufacturer recommended surface speed (Vc) for your material.
  2. Specify tool cutting diameter and flute count.
  3. Provide desired chip load per tooth (fz).
  4. Optionally supply axial and radial cut depths to calculate volumetric MRR.

Step-by-Step Example Calculation

12mm 4-Flute Endmill in Mild Steel (Vc = 150 m/min)

Input Values:

cuttingSpeedVcMPerMin:150
cutterDiameterMm:12
fluteCount:4
feedPerToothFzMm:0.06
depthOfCutApMm:5.0
widthOfCutAeMm:6.0
Worked Steps: Optimal spindle speed is 3,979 RPM with a 955.0 mm/min table feed rate, yielding a Material Removal Rate of 28.65 cm³/min.

Understanding Your Result

Spindle Speed (RPM): Commanded CNC spindle rotational velocity.

Table Feed Rate (mm/min): G-code linear axes travel rate (F-word).

Feed Per Rev (fn): Table advance per single spindle revolution.

MRR (cm³/min): Volumetric metal removal rate for power checks.

Factors That Affect the Result

  • Tool material (HSS vs solid carbide), workpiece hardness, coolant application, and machine rigidity.

When Should You Use This Calculator?

  • CAM programming (Fusion 360, Mastercam), machine shop tool setups, and CNC tooling cost optimization.

Assumptions & Limitations

  • Assumes conventional constant-engagement toolpaths without radial chip thinning compensation on very shallow stepovers (ae < 20% D).

Frequently Asked Questions

Calculation Accuracy & Reference Note

Standard DIN / ISO manufacturing speeds and feeds kinematic equations.

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