Speeds and Feeds Calculator
Work out spindle speed (rpm) and feed rate for milling, drilling and turning from the material, tool and diameter. HSS and carbide.
New: please check your results.
For guidance only. This is not a substitute for a qualified engineer, and important designs should be checked by one.
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- Spindle speed
- 2,865 rpm
- Feed rate
- 286.5 mm/min
- Cutting speed used
- 90 m/min
What it does
Find the spindle speed and feed rate for a milling, drilling or turning job. Choose the material and the tool (HSS or carbide), enter the diameter and the feed per tooth or per revolution, and get the rpm and the feed in mm/min or in/min. The built-in cutting speeds are safe starting points; adjust by sound, chips and finish.
How to use it
- Operation
For milling and drilling the tool spins; for turning the workpiece spins.
- Tool diameter
The diameter of the end mill, cutter or drill.
- Workpiece diameter
The diameter being cut. For facing, use the largest diameter; the speed should rise as you move to the centre.
- Material
The material being cut. Each has a typical cutting speed: how fast the cutting edge can move through it.
- Tool material
HSS (high speed steel) or carbide. Carbide tools can cut about three to four times faster than HSS, on a rigid machine.
- Cutting speed
From the tool maker's data: in m/min (metres per minute) or SFM (surface feet per minute).
- Number of flutes (teeth)
2 or 3 flutes for aluminium and plastics, 3 or 4 for steel.
- Feed per tooth
How thick a chip each tooth takes. For a 10 mm end mill, about 0.03 to 0.08 mm in steel and 0.05 to 0.1 mm in aluminium. Smaller cutters need less.
- Feed per revolution
How far the tool advances each turn. Drilling: roughly 1% of the drill diameter (0.1 mm for a 10 mm drill). Turning: 0.1 to 0.3 mm for roughing, 0.05 to 0.1 mm for finishing.
Common uses
- Setting up a milling machine or CNC router for a new material.
- Choosing a drill press speed for a large drill.
- Setting lathe speed for a bar of a given diameter.
- Finding the tap drill for a threaded hole. Try the Tap Drill Size Calculator
- Working out pulley or gear ratios for spindle speeds. Try the Gear Ratio Calculator
The formula
rpm = (cutting speed × 1,000) ÷ (π × diameter in mm) (cutting speed in m/min)rpm = (SFM × 12) ÷ (π × diameter in inches) (SFM in ft/min)Milling feed = rpm × flutes × feed per toothDrilling and turning feed = rpm × feed per revolutionWhere:
- Cutting speed
- how fast the cutting edge moves through the material (surface speed)
- diameter
- of the tool for milling and drilling, of the workpiece for turning
Starting cutting speeds (m/min, HSS / carbide): aluminium 90 / 300, brass 60 / 180, plastics 60 / 150, mild steel 30 / 120, cast iron 20 / 90, alloy and tool steel 15 / 80, stainless steel 12 / 70. Reduce them for small or old machines, long tools, no coolant or interrupted cuts.
Worked example
Milling aluminium with a 10 mm HSS end mill with 2 flutes:
- Cutting speed for aluminium with HSS: 90 m/min
- Spindle speed: (90 × 1,000) ÷ (π × 10) = 2,865 rpm
- Feed: 2,865 rpm × 2 × 0.05 mm = 286.5 mm/min
Questions people ask
What speed should I drill steel at?
With an HSS drill in mild steel, about 30 m/min: roughly 950 rpm for a 10 mm drill, 1,900 rpm for 5 mm and 600 rpm for 16 mm. Halve that for stainless steel, and use cutting fluid for both.
My machine can't reach the rpm it says. What now?
Run at the machine's top speed and work out the feed from that rpm instead: feed = rpm × flutes × feed per tooth. Keeping the chip load (feed per tooth) right matters more than the exact speed; too light a feed rubs and blunts the tool.
How do I know if the speeds and feeds are right?
Watch the chips and listen. In steel, chips should be curled and straw to light-blue coloured, not dark blue or powder. Squealing or chatter means slow down or feed harder; a burnt or smeared finish means too fast or too little feed.
Last checked 4 November 2026 · Last rev. 31 October 2026 · 67d4