Machining time calculator
Estimate the cycle time of a CNC machining operation from machining length, feed rate, and number of passes. Practical for an initial calculation basis — for binding quotes, a CAM simulation is recommended.
The allowance covers rapids, approaches and short stops. It does not replace a CAM simulation.
Estimated time
Note: All values are non-binding reference figures. Actual values depend on machine, tool, material and conditions. Start conservatively. No liability is accepted for tool breakage, machine damage or machining results.
What the Machining Time Calculator Works Out
The calculator estimates the net cutting time of a CNC machining operation from the machining length, feed rate and number of passes. You can also add an allowance for rapid traverses and approach moves and calculate the total time for a given quantity. The result is a quick first basis for costing, but not a substitute for a real CAM simulation.
The Formula
t = (s / vf) × n × (1 + Z/100)
Here, t is the machining time, s is the machining length in mm, vf is the feed rate in mm/min, n is the number of passes and Z is the allowance in percent for rapid traverses and approach moves. Example: a machining length of 2000 mm at a feed rate of 3000 mm/min and one pass gives a net cutting time of 2000 / 3000 = 0.667 min. With a 15% allowance, that is around 46 seconds.
What the Estimate Does Not Include
- Tool changes: Each change takes several seconds to several minutes, depending on the machine. With many tools, this adds up.
- Setup and clamping time: Loading, aligning and clamping the workpiece. This varies greatly with the component and fixture.
- Acceleration and braking: With very short path segments or tight radii, the machine often never reaches the programmed feed rate. The actual time is then longer than calculated.
- Tool changes due to wear: For long machining operations, additional tool life breaks may be needed.
What the Estimate Is Suited For
The formula is well suited to rough quote costing, comparing different feed strategies or a first plausibility check, especially for simple, straight or evenly curved paths. For complex 3D contours with many short segments, CAM software (which simulates the actual path including acceleration ramps) gives much more accurate values.
Frequently Asked Questions
How accurate is the calculated machining time?
The formula gives the net cutting time plus a flat allowance for rapid traverses. This is a guide value, not an exact prediction. Tool changes, setup time and the machine’s braking behaviour on short path segments are not included. For a binding quote, CAM software simulates the actual tool path.
What allowance should I plan for rapid traverses?
That depends heavily on the component. For a single long contour, 5–10% is often enough; for many short pockets or holes with frequent approach moves, 20–30% may be more realistic. The default value of 15% is an average for mixed machining operations.
Why is the actual time on the machine often longer than calculated?
Besides tool changes and setup time, this is often down to acceleration: with short path segments or tight radii, the controller slows down before the programmed feed rate is even reached. The more changes of direction a contour has, the greater the deviation from the simple path-divided-by-feed calculation.
Can I also use it to calculate the time for several workpieces?
Yes. Using the “Quantity” field in the expandable “Include allowances” section, the calculator multiplies the time per workpiece by the required quantity and also shows the total time. Tool changes between workpieces are not included.
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