Speed and Feed Engineering Calculator – Kennametal

These calculations are based upon theoretical values and are only intended for planning purposes. Actual results will vary. No responsibility from Kennametal is assumed.

Surface Feet Per Minute

Surface Feet Per Minute (SFM)

in mm


SFM m per min
Inches per minute (IPM)

Inches per minute (IPM)



Revolutions per minute (RPM)

Revolutions per minute (RPM)

in mm


Calculate Metric To Inches

Calculate Metric To Inches

mm per rev or mm


in / rev. or in.
Calculate Inches To Metric

Calculate Inches To Metric

in / rev. or in.


mm per rev or mm

How to Find Speeds and Feeds

Create Solution to calculate Feeds & Speeds for your application. After creating a solution just choose the Feeds & Speeds icon and our system will provide recommendations.

Speed and Feed Calculator FAQ

Speeds and feeds are one of the most important elements for achieving the best results for drilling, holemaking, and milling operations. Improper speeds and feeds often cause low production, poor quality, and damage to the cutting tool. Kennametal’s speeds and feeds calculator streamlines the calculation of rates using either the metric or English system of weights and measures. It allows you to accurately determine surface feet per minute, inches per minute, or revolutions per minute. If this calculator does not give you the results you need for your specific application, our application specialists can help you calculate speed and feed rates correctly.

How do you calculate speed and feed?

Speed (RPM) = (Surface Feet per Minute x 3.82) / Diameter of the Tool  

Feed Rate = RPM x Chip Load x Number of Teeth

RPM = Of the tool or workpiece

Chip Load = The amount of material removed, per revolution per cutting edge

Number of Teeth = The number of edges, facets, or flutes.

What RPM should you mill steel?

Multiple factors affect the spindle speed (RPM) when milling steel, these include:

The type of steel:

  • Overall hardness
  • Heat treatment
  • Alloying composition

The type of tooling:

  • Material (high-speed steel, carbide, etc.)
  • Shape
  • Condition (new vs worn)

The type of milling machine:

  • Use of coolant
  • Stability of work holding fixtures 

Most specialty steel manufacturers will make available machining information if it is not a common steel variant.  

How does a CNC mill calculate speeds and feeds or SFM?

A CNC mill calculates speeds and feeds or SFM based on the information the user enters. The type of CNC mill, the type of machine controller, and the age of the machine will affect the amount of information that can be input directly into the machine. Historically G-code was created externally from a CNC machine and then loaded onto the machine. Externally created G-code was authored either with a dedicated CAM software or with a plug-in embedded in the 3D parametric modeling software. The user would input the same CNC machine they want to create the part on (with the specific work holding fixture), the type of tooling (manufacture, part number etc.), and the specific material being machined. The software generates the speeds and feeds based on the part's geometry and all the inputted information. This creates the optimal speeds and feeds or SFM tailored to the exact part and CNC machine.    

How do you calculate feed for turning?

Turning Feed Rate = Rotational Speed (N) x Feed Rate (fr)

Rotational Speed (N) = Cutting Speed (SFM) / π x Original Diameter 

Feed Rate (fr) = Rotational Speed (N) x Feed (f). Note: Feed (f) is in distance/revolution.  

How do you calculate SFM in machining?

Milling Surface Feet per Minute = (RPM x Tool Diameter) / 3.82

Turning Surface Feet per Minute = 0.262 x Part Diameter x RPM

How does SFM calculate RPM?

Surface Feet per Minute = (RPM x Circumference) / 12  

Note: The circumference unit is in inches and is dependent on if it’s a milling or turning operation. For milling operations, the circumference is of the cutter (tool in the spindle). For turning operations, the circumference is of the workpiece (the material in the chuck).

What is Surface Feet Per Minute (SFM)?

Surface feet per minute (SFPM or SFM) is the combination of a physical quantity (surface speed) and an imperial and American customary unit (feet per minute or FPM). It is defined as the number of linear feet that a location on a rotating component travels in one minute.

What is Inches per minute (IPM)?

Inches per minute (IPM) is a speed measurement of how many inches traveled in a minute, without regard to direction. In machining, it is primarily used as a feed rate (imperial units).  

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