CNC Feeds and Speeds Calculator

Formula

• n = (Vc × 1000) / (π × D)
• Milling: Vf = n × fz × Z, MRR = ap × ae × Vf / 1000 (cm³/min)
• Turning: Vf = n × f, MRR = DOC × f × Vc × 1000 / (π × D)

About this calculator

Part of our Machining & CNC Calculators collection. Cutting speed, feeds, RPM, cycle time, and tap drill charts.

How it works

Spindle speed and feed rate follow standard Vc and chip load relationships. Material removal rate uses axial and radial depth for milling or depth of cut for turning. Cutting power estimates machine load from MRR and specific cutting force.

Enter your values in the inputs above and click CALCULATE. Results appear on the right without a page reload. No login and no server upload.

Worked example

Milling: Vc = 150 m/min, 12 mm cutter, fz = 0.12, 4 flutes, ap = 3, ae = 6 mm.

1. RPM = 3,979
2. Feed = 3,979 × 0.12 × 4 = 1,910 mm/min
3. MRR = 3 × 6 × 1,910 / 1000 = 34.4 cm³/min

Result: 3,979 RPM, 1,910 mm/min feed, 34.4 cm³/min MRR, ~1.2 kW cutting power.

When to use

• Programming CNC mill or lathe feeds and speeds with MRR
• Estimating cutting power for machine load checks
• Comparing milling vs turning removal rates

Limitations

• Cutting power uses simplified kc / material factor models
• Does not check spindle torque or machine rigidity limits
• Radial/axial depths assumed constant over the cut

FAQ

How is MRR different from the simple milling calculator?

This tool adds axial and radial depth to compute volumetric removal rate and estimated cutting power, not just RPM and feed.

What material factor should I use for milling?

Start at 1.0 for mild steel. Increase for stainless or hard alloys; decrease for aluminium. Tune against machine load meter readings.

Why show actual cutting speed?

Integer RPM slightly changes true Vc. Actual Vc shows what the machine delivers after rounding spindle speed.