Feeds and Speeds Calculator
Spindle speed from cutting speed and tool diameter, feed rate from chip load and flutes, the material removal rate that follows, the spindle power it needs and the time to cut a given length — the four numbers every CNC program starts with.
The tool's edge must move through the material at the cutting speed the material and coating are rated for; for a given diameter that fixes the spindle speed.
How the feeds and speeds calculator works
The tool's edge must move through the material at the cutting speed the material and coating are rated for; for a given diameter that fixes the spindle speed. Each flute should take a chip of a set thickness, so feed rate is speed times flutes times chip load. Depth and width of cut then give the volume removed per minute, and the material's specific cutting energy turns that into power — which is what tells you whether the machine can do it.
Formula: n = 1000 V_c / (π D); v_f = n z f_z; MRR = a_p a_e v_f / 1000; P = MRR × k_c / 60
Worked examples
| Inputs | Spindle speed (rpm) | Note |
|---|---|---|
| A 10 mm end mill in steel | 4,775 | about 4,800 rpm |
| Aluminium, faster and lighter | 12,732 | past 12,000 rpm |
| A 3 mm cutter | 15,915 | rpm-limited |
FAQFrequently asked questions
What is cutting speed?
The speed of the tool's edge through the material, in metres per minute, set by the material and the tool coating: 100 to 200 for steel with carbide, 300 to 600 for aluminium. The tool maker publishes it.
What is chip load?
The thickness of material each flute removes per revolution. Too little rubs and work-hardens; too much breaks the tool. Typically 1 to 2% of the tool diameter.
Why does power matter?
Because a small machine cannot sustain the removal rate the tool could take. Specific cutting energy is around 0.7 J/mm³ for aluminium, 2 to 3 for steel, 4 or more for titanium.
What if the rpm exceeds the machine?
Run at the maximum and accept a lower cutting speed; the page recomputes the feed from the capped rpm. A smaller tool needs more rpm than a larger one.
Does chip thinning apply?
At radial widths under half the diameter the real chip is thinner than the nominal load, and feed can rise. This page uses the nominal load; apply a thinning factor for light radial cuts.
Where these figures come from
- Nakajima (1988) — Introduction to TPM — the origin of Overall Equipment Effectiveness and its six big losses
- Safe Work Australia — the national work health and safety body
Last checked: September 2026. Definitions follow standard operations-management practice; where plants commonly differ, the page says so.