Machining Speed & Feed Calculator
Calculate spindle speed (RPM), feed rate, feed per revolution and material removal rate for milling, in metric or imperial units — with starting cutting speeds and chip loads built in for 13 workpiece materials.
Input
Metric: diameter in mm, cutting speed in m/min, feed in mm/min. Imperial: diameter in inches, cutting speed in SFM, feed in in/min.
Cutter diameter — millimetres in metric mode, inches in imperial mode.
Supplies the starting cutting speed and chip load when the two fields below are left blank.
m/min in metric mode, surface feet per minute (SFM) in imperial mode. Leave blank to use the material's recommended starting speed.
mm/tooth in metric mode, inch/tooth in imperial mode. Leave blank to derive it from the material's chip-load percentage of cutter diameter.
Only used to compute the material removal rate. Same length unit as the tool diameter.
Only used to compute the material removal rate. Same length unit as the tool diameter.
Output
| Metric | Value |
|---|---|
| No data yet | |
Guides
What this calculator does
It turns a cutter and a workpiece material into the two numbers a machine actually needs: spindle speed in RPM and feed rate. It also reports feed per revolution, the cutting speed and chip load it used, and — if you give it a depth and width of cut — the material removal rate.
Unlike most speeds-and-feeds calculators, the cutting speed (Vc) and feed per tooth (fz) fields are optional. Leave them blank and the tool fills in a sensible starting value for the workpiece material and tool material you picked, so you can get usable numbers from nothing but a diameter and a flute count.
The formulas
Metric:
- Spindle speed:
n = Vc × 1000 ÷ (π × D)— Vc in m/min, D in mm - Feed rate:
Vf = n × Z × fz— mm/min - Removal rate:
MRR = ap × ae × Vf ÷ 1000— cm³/min
Imperial:
- Spindle speed:
n = SFM × 12 ÷ (π × D)— D in inches - Feed rate:
Vf = n × Z × fz— in/min - Removal rate:
MRR = ap × ae × Vf— in³/min
How to use it
- Pick metric or imperial. Every length field follows that choice — millimetres and m/min, or inches and surface feet per minute.
- Enter the tool diameter and the number of teeth (flutes) on the cutter.
- Choose the workpiece material and whether the tool is carbide or HSS.
- Leave Vc and fz blank to use the built-in starting values, or type your tooling vendor's figures to override them.
- Optionally add the axial depth (ap) and radial width (ae) of the cut to get a removal rate.
Where the recommended numbers come from
The cutting speeds are conservative general-milling starting points for each material class — the kind of figure a shop reference gives you before you consult a specific insert's data sheet.
Feed per tooth is not a fixed number per material; it is calculated as a percentage of cutter diameter (2% for aluminium, 1% for mild steel, 0.5% for nickel alloys, and so on). That is the standard rule of thumb, and it is why the same material gives a much smaller chip load on a 3 mm cutter than on a 12 mm one.
Are these numbers safe to run straight into a machine?
Treat them as a starting point, not a prescription. Real speeds and feeds depend on your machine's rigidity and power, the tool's stick-out, coolant, coating and the specific alloy. Always sanity-check against your tooling manufacturer's data and step up gradually.
Why doesn't it apply chip thinning?
Radial chip thinning matters once your radial width of cut drops well below half the cutter diameter, and the correction depends on the exact tool geometry. This calculator reports the programmed feed rather than guessing a compensation factor for you — if you are cutting at a small stepover, expect to increase fz above the value shown here.
Does it work for turning as well as milling?
The spindle-speed formula is identical for turning — just use the workpiece diameter instead of the tool diameter, and set teeth to 1. The feed rate then reads as feed per revolution, which is how turning feeds are normally specified.
Privacy
Everything is calculated in your browser. No dimensions, materials or job details are sent anywhere.
Related tools
For the mechanical side of the job, the Bolt Torque Calculator sizes tightening torque for fasteners, and the Unit Converter handles any millimetre-to-inch conversion this tool doesn't cover directly.