MachiningCalc / Lathe Speeds & Feeds Calculator

Turning · lathe calculations

Lathe Speeds & Feeds Calculator

Calculate turning spindle speed from workpiece diameter and SFM, then convert feed per revolution into IPM and estimate material removal rate.

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Calculator

Enter your known cutting data. Results update automatically.

Spindle speed—
Linear feed—
Estimated MRR—
Surface speed—

Use manufacturer cutting data and stay within machine, tool and workholding limits.

Calculation check: Turning uses the current work diameter for RPM. The MRR estimate uses 12 × SFM × DOC × IPR in inch units.
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US unitsInches, SFM, RPM, IPM
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Calculation method

How this calculator works

RPM = SFM × 12 ÷ (π × Work Diameter)IPM = RPM × Feed per RevolutionMRR ≈ SFM × 12 × DOC × Feed per Revolution

Values are deterministic outputs from the inputs shown above; cutting recommendations are not inferred.

Why work diameter matters on a lathe

At constant surface speed, RPM changes with diameter. This is especially relevant as a turning or facing cut moves across changing diameters.

Turning MRR

The material-removal estimate follows the standard inch-unit relationship between cutting speed, radial depth of cut and feed per revolution. Treat it as a planning value rather than a spindle-load model.

Technical references