Turning Speed and Feed Calculator – RPM and IPM Calculation Formula for CNC Turning

How to calculate turning speed and feed? The Turning Speed and Feed Calculator is a great tool to calculate spindle speed and feed rate for turning operations, as well as the cut time expressed in minutes. Enter the required value and the result will be displayed. You can keep a record of the RPM and IPM calculation formula for turning or come to CNCLATHING.COM at any time to use the CNC turning calculator, or Milling Speed and Feed Calculator and Drilling Speed and Feed Calculator based on your needs, the rapid calculation can help you save time and reduce errors, therefore determine right speed and feed for the lathe turning applications.


  1. The RPM calculated in the Turning(Lathe) Speed and Feed Calculator refers to the spindle speed in turning process, and the IPM refers to feed rate.
  2. The exact RPM is not always needed, the following calculator (formula) may be used to estimate the value closely.
  3. Cutting speed (SFM): the rate at the workpiece surface, measured in surface feet per minute, irrespective of the machining operation used.
  4. Cut diameter and Cut length in this calculator in inches.
  5. The turning RPM and IPM calculations use the desired cut diameter, cutting speed, and cutting feed, which should be chosen based on the specific cutting conditions, including the workpiece material and tool material.
  6. In some turning operations, the diameter of the workpiece will change so the spindle speed and cutting speed must change as well.
  7. Typically, values are calculated for a single cut diameter and then either the spindle speed or cutting speed is held constant while the other varies.
Turning Speed and Feed Calculator

Turning Speed and Feed Calculator

× 12
× π



Understand Spindle Speed and Feed Rate – What is Turning Spindle Speed (RPM)?

The spindle speed is the rotational frequency of the spindle of the machine, such as milling machine, lathes, drills, and routers, measured in revolutions per minute (RPM). The preferred speed is determined by working backward from the desired cutting speed (SFM or m/min), which may be defined as the rate at the workpiece surface, and incorporating the diameter of cutter or workpiece. CNC turning is a computer-controlled manufacturing process in which bars of material are held in a chuck and rotated while a cutting tool is fed to the workpiece to remove excess material to create designed CNC turned parts. In turning operation, the cut diameter is used.

Understand Spindle Speed and Feed Rate – What is Turning Feed Rate (IPM)?

Feed rate is the velocity at which the cutter is fed, or the rate advanced against the workpiece, often expressed in units of distance per revolution for turning, that typically is inches per revolution (IPR) or millimeters per revolution (MPR). Turning feed rate is determined by the type of cutting tools, surface finish desired for milling parts, power available at the spindle, rigidity of the machine and tool setup, characteristics of the material to be cut, workpiece strength, cut width, etc.

The Importance of Turning Speed and Feed Calculations

The spindle speed is derived from cutting feeds and speeds, it is one of the ideal cutting conditions for a tool, if the condition is not ideal, the adjustment of spindle speed is necessary, usually reduce in RPM or modify it to a correct value. Some materials can be cut at a wide range of spindle speeds, while cutting speed is critical to some materials like stainless steel, it’s easy to harden under cold working, then resist the tool’s cutting action. When choosing which feed rate to use, the calculation for turning is fairly easy, because it uses single-point cutting tools and all of the cutting work is done at one point. Insufficient feed rate or incorrect spindle speed will cause improper cutting conditions, therefore it’s important to figure out the CNC turning speeds and feeds with our turning spindle speed and feed rate calculator and control it carefully to avoid overheating of the cutter and workpiece.

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Turning Speed and Feed Calculator