CNC machining time calculator

Example result

With 6 in³ of stock removed, 40 in² finished area, 6 holes (4 tapped), 3 inches of hole depth, and 2 setups, the formula returns 11.2 minutes per part.

Use it carefully

The formula does not know tool changes, workholding surprises, probing, chip evacuation, operator interruptions, or a specific machine's limits. Treat the output as a documented starting assumption, then replace it with a CAM cycle or a shop's measured history when the job matters. It is useful because it makes the approximation inspectable: another estimator can see which term drove the result and challenge that term instead of arguing about one unexplained total.

A drawing-only estimate should also carry the confidence of the dimensions. If a pocket depth or hole depth is inferred, mark it as an assumption and ask for the missing information before promising a delivery date. The calculator supports a conversation with a programmer; it does not replace the programmer's toolpath.

• Use the same units and material assumption throughout.
• Count setups explicitly; a flip is not free.
• Keep the formula and inputs beside the quote so a later reviewer can change them.

Inputs worth recording

Record the material and the geometry facts beside the result. Removed volume is stock minus finished part volume; finished area is the area that receives a finishing pass; hole depth is the sum of the drilled depths. If any of those values came from a rough drawing read, say so and give the programmer a chance to replace it.

• Material machinability changes the roughing and finishing terms.
• A larger tool scale lowers the default removal and finishing rates.
• The number of setups adds load and unload time and affects the routing.