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Speeds and Feeds Calculator
Calculate spindle RPM and feed rate for machining from cutting speed and tool parameters.
m/min
mm
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CNC Speeds and Feeds
Spindle speed is found from the desired cutting speed and tool diameter: N (RPM) = (Vc × 1000) / (πD), where Vc is cutting speed in meters per minute and D is tool diameter in millimeters. Feed rate then follows from Vf = N × fz × z, where fz is the feed per tooth (chip load) and z is the number of cutting flutes.
Cutting speed depends on the tool material and the workpiece material being machined — carbide tools in aluminum can run much faster than HSS tools in hardened steel. Getting speeds and feeds right balances tool life, surface finish, and cycle time; this calculator gives the standard starting-point values used in machine shop reference charts.
Last reviewed August 2026