Machining Time Calculator
Cycle time for a milling or turning job from the length of cut, approach and overtravel, feed rate and number of passes, with allowances for rapids, tool changes and load and unload. Get minutes per part, time for the lot with setup, and machine cost at your shop rate. Take the feed rate from the speeds and feeds calculator or enter your own.
Cycle time & machine cost
Need a feed rate? Get one from the speeds and feeds calculator.
Enter a length of cut, feed rate and number of passes for each operation. Rapids, tool changes, load and setup are optional.
Machine time only: it leaves out material, programming, inspection, finishing and margin, so it is not a quote.
Checking a quote or planning capacity? Send the drawing and , or browse CNC machining shops.
The formulas
- Cutting time per operation: T = passes x (length of cut + approach + overtravel) / feed rate
- Cycle time per part: sum of cutting times + rapids allowance + tool changes x seconds each + load and unload
- Lot time: cycle time x quantity + setup
- Machine cost: minutes / 60 x shop rate per hour
Worked example: three passes along a 4.0" edge with 0.1" approach and 0.1" overtravel at 20 in/min take 3 x 4.2 / 20 = 0.63 min. Add 10 seconds of rapids and two tool changes at 8 seconds and the cycle is 0.63 + 0.17 + 0.27 = 1.06 min. Ten parts plus a 30 minute setup is 40.6 min, or $64.34 of machine time at $95 an hour.
Length and feed only need to share a unit: inches with in/min or millimeters with mm/min give the same minutes.
What the estimate leaves out
- Acceleration: short moves, small arcs and corners run below the programmed feed.
- Rapids at less than full traverse, spindle ramp-up and dwells.
- In-process probing, chip clearing and tool breakage checks.
- Deburring, inspection and anything that happens off the machine.
Getting closer to the real number
- Time the first part and scale the per-part minutes rather than trusting the arithmetic.
- Use the CAM system's cycle time with the machine's real acceleration settings when you have it.
- Face mills need about half the cutter diameter plus clearance at each end to clear the part.
- Count every pass: roughing, semi-finishing, finishing and spring passes.
Frequently asked questions
- How do you calculate machining time?
- Cutting time for one pass is the distance the tool travels at feed divided by the feed rate: (length of cut + approach + overtravel) / feed. Multiply by the number of passes, add up the operations, then add the non-cutting time: rapids, tool changes and load and unload. Four passes over 5 inches at 20 in/min is 1.0 minute of cutting.
- What are approach and overtravel?
- Approach is the distance the tool moves at feed before it touches the part, and overtravel is the distance past the end of the cut before it stops or retracts. Both cost time at the feed rate. A face mill that has to clear the part needs about half its diameter plus a little clearance on each end; an end mill ramping into a profile needs much less.
- Why is the real cycle time longer than the calculation?
- Machines accelerate and decelerate, so short moves and tight corners never reach the programmed feed, and rapids are rarely at full traverse. Spindle ramp-up, dwells, probing, coolant and chip clearing add more. Timing a first part or running the program through a CAM simulator with the machine's real acceleration closes the gap.
- Is machine time the price of the part?
- No. Machine time at a shop rate is one piece of the price. Material, programming, setup, fixturing, inspection, finishing, packaging and margin all sit on top, and a shop quoting a lot spreads setup across the quantity. Use the machining cost estimator for a whole-part ballpark, or send the drawing for a real quote.
