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All calculatorsMethodology

Feeds and Speeds Calculator

Turn a cutting speed and chip load from your tooling data into spindle RPM and feed rate, in inch (SFM, IPM) or metric (m/min, mm/min), with an RPM cap.

Interactive calculator · Method FEEDS-AND-SPEEDS-1.0 · Last reviewed: 2026-11-04

Calculate your scenario

Inch: RPM = SFM × 12 ÷ (π × diameter in inches).

Your inputs

Try an example

Default worked example. Edit the inputs to calculate your scenario.

Default worked example

Spindle speed to use 2,292 RPM
Calculated spindle speed before cap 2,291.8 RPM
Feed rate 18.33 in/min
Actual surface speed 300 SFM
Feed per revolution 0.008 in/rev

RPM = 300 SFM × 12 ÷ (π × 0.5 in) = 2,291.8; feed = 2,291.8 × 4 × 0.002 = 18.33 in/min.

How to use the calculator

Pick inch or metric, enter the tool diameter (or workpiece diameter for turning), the cutting speed and chip load from your tooling data, the tooth count and your spindle’s maximum RPM.

What the result means

A 0.5 in four-flute tool at 300 SFM needs about 2,292 RPM; at 0.002 in per tooth that is about 18.33 in/min.

Formula and units

Inch: RPM = SFM × 12 ÷ (π × diameter in inches). Metric: RPM = Vc (m/min) × 1,000 ÷ (π × diameter in mm). If the result exceeds the machine maximum, the maximum is used. Feed rate = RPM × number of teeth × chip load per tooth, and actual surface speed = π × diameter × RPM ÷ 12 (or ÷ 1,000).

Worked examples

0.5 in four-flute end mill at 300 SFM: Tool or workpiece diameter: 0.5 in or mm; Cutting speed from tooling data: 300 SFM or m/min; Number of flutes or teeth: 4 teeth; Chip load per tooth from tooling data: 0.002 in or mm per tooth; Machine maximum spindle speed (0 = no cap): 10000 RPM; Unit system: inch.
Example result: Spindle speed to use: 2,292 RPM; Calculated spindle speed before cap: 2,291.8 RPM; Feed rate: 18.33 in/min; Actual surface speed: 300 SFM; Feed per revolution: 0.008 in/rev.

12 mm three-flute tool at 100 m/min: Tool or workpiece diameter: 12 in or mm; Cutting speed from tooling data: 100 SFM or m/min; Number of flutes or teeth: 3 teeth; Chip load per tooth from tooling data: 0.05 in or mm per tooth; Machine maximum spindle speed (0 = no cap): 10000 RPM; Unit system: metric.
Example result: Spindle speed to use: 2,653 RPM; Calculated spindle speed before cap: 2,652.6 RPM; Feed rate: 397.89 mm/min; Actual surface speed: 100 m/min; Feed per revolution: 0.15 mm/rev.

Limitations and common mistakes

Arithmetic only. Cutting speed and chip load must come from the tool maker’s data for your tool, material and operation; this does not recommend values. Radial chip thinning, tool deflection, rigidity, coolant, depth of cut and machine power are not modeled.

Leaving the feed at the uncapped value after the spindle tops out; that raises the real chip load. Recalculate feed from the RPM the machine can actually run.

Sources and assumptions

Method FEEDS-AND-SPEEDS-1.0; last formula review 2026-11-04. Sources and their supported claims. Calculation methodology.