Work out spindle speed (RPM) and feed rate for milling or drilling. Pick the workpiece and tool material to start from typical values, or enter your own surface speed and chip load, in metric or imperial units. Optional inputs add material removal rate, chip thinning and cycle time.
Last updated:
Units
Operation
mm
in
RPM is capped at this limit
Surface speed and chip load
m/min
SFM
mm/tooth
in/tooth
Optional: cut size and time
mm
mm
mm
in
in
in
Enter your values to see the result.
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How to use the Speeds and Feeds Calculator
Choose units and operation: metric or imperial, milling or drilling.
Select the workpiece and tool material and enter the tool diameter and number of flutes.
Use the typical values or switch to entering your own surface speed and chip load from the tool maker's catalogue.
Optionally add width and depth of cut and a cut length for material removal rate and time.
Read RPM and feed, then fine-tune on the machine by listening to the cut and checking the chips.
Speeds and feeds formulas
Quantity
Metric
Imperial
Spindle speed
RPM = Vc × 1000 ÷ (π × D)
RPM = SFM × 12 ÷ (π × D) ≈ 3.82 × SFM ÷ D
Feed rate
Vf (mm/min) = RPM × z × fz
IPM = RPM × z × chip load
Feed per revolution
fn = z × fz (mm/rev)
IPR = z × chip load
Material removal rate
Q = ae × ap × Vf ÷ 1000 (cm³/min)
MRR = WOC × DOC × IPM (in³/min)
Surface speed from RPM
Vc = π × D × RPM ÷ 1000
SFM = π × D × RPM ÷ 12
D = tool diameter, z = number of flutes, fz = chip load per tooth, ae = radial width of cut, ap = axial depth of cut.
Typical starting surface speeds
Workpiece material
HSS (SFM)
Carbide (SFM)
Carbide (m/min)
Aluminum alloys
250–600
600–1,200
183–366
Brass / bronze
150–300
300–600
91–183
Plastics
300–600
500–1,000
152–305
Mild steel (1018)
80–110
300–500
91–152
Alloy steel (4140)
50–80
250–400
76–122
Stainless steel (304/316)
40–70
200–350
61–107
Gray cast iron
60–100
250–400
76–122
Titanium (Ti-6Al-4V)
25–45
100–200
30–61
These conservative ranges are for uncoated or general-purpose tools in a reasonably rigid machine. Coated carbide and high-performance toolpaths can run much faster; follow your tool supplier's recommendations.
Frequently asked questions
How do I calculate spindle RPM?
RPM = (Vc × 1000) ÷ (π × D) with cutting speed Vc in m/min and diameter D in mm, or RPM = (SFM × 12) ÷ (π × D) ≈ 3.82 × SFM ÷ D with D in inches. For example 250 m/min with a 10 mm cutter gives about 7,958 RPM.
How do I calculate the feed rate?
Feed rate = RPM × number of flutes × chip load (feed per tooth). A 3-flute end mill at 8,000 RPM with 0.05 mm per tooth feeds at 8,000 × 3 × 0.05 = 1,200 mm/min.
What is chip load?
Chip load (feed per tooth, fz) is the thickness of material each cutting edge removes per revolution. Too small and the tool rubs and work-hardens the material; too large and it can chip or break. Tool manufacturers publish recommended chip loads by diameter and material.
What is surface speed (SFM)?
Surface speed is how fast the cutting edge moves past the material, in metres per minute (Vc) or surface feet per minute (SFM). It depends mainly on the workpiece and tool material: aluminium tolerates very high speeds, titanium and stainless steel need low speeds.
What is chip thinning?
When the radial width of cut is less than half the tool diameter, the actual chip is thinner than the programmed feed per tooth. To keep the intended chip thickness you can raise the feed by the factor 1 ÷ √(1 − (1 − 2ae/D)²), shown when you enter a width of cut.
Are the suggested values safe to use?
They are conservative textbook starting points, not guarantees. Always check the cutter manufacturer's data and consider machine rigidity, workholding, tool stick-out, coolant and coatings; start lower and increase while watching the chips and listening to the cut.
Why is drilling speed lower?
Drills cut with their full diameter at the bottom of the hole, chip evacuation is harder and heat builds up, so they are usually run toward the low end of the material's speed range with a feed per revolution rather than a high feed per tooth.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.