Cutting Speed Calculator

Work out cutting speed instantly with clear inputs, formula shown and shareable results.

About Cutting Speed Calculator

Cutting speed is the surface velocity where the tool meets the work: pi times diameter times rpm, divided by 12 to give feet per minute. Every tool material has a recommended range, so knowing the speed a given diameter and rpm produces is what lets a handbook figure be applied to the machine in front of you.

Formulas

Cutting speed

SFM = pi x D in x rpm / 12

Inverse

rpm = 12 x SFM / (pi x D)

Worked example

With the default values below, Cutting Speed Calculator returns Cutting speed of 209.4. Change any input above and every figure here is recalculated in your browser.

Inputs used

Tool or workpiece diameterminimum 0.01 in: 1 in
Spindle speedminimum 1 rpm: 800 rpm

Results

Cutting speed: 209.4 SFM
Cutting speed in metric units: 63.84 m/min
Cutting circumference: 3.142 in
Speed for 300 SFM: 1,146 rpm

Step by step

1Values used
2Cutting speed
3Inverse
4Cutting speed= 209.4 SFM
5Cutting speed in metric units= 63.84 m/min
6Cutting circumference= 3.142 in
7Speed for 300 SFM= 1,146 rpm

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Cutting Speed figure worked out?

SFM = pi x D in x rpm / 12. Cutting speed is the surface velocity where the tool meets the work: pi times diameter times rpm, divided by 12 to give feet per minute.

Why does a small drill need high rpm?

Surface speed depends on diameter. A 1/8 inch drill at 800 rpm cuts at only 26 SFM, far below the recommended range, so small tools must spin much faster to reach the same cutting speed.

What values do I need to enter?

This calculator takes 2 inputs: Tool or workpiece diameter, Spindle speed. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.