The basic machining-time formula divides distance by feed rate. A useful planning estimate adds approach distance, repeated passes, rapid moves, and tool-change time while still separating those modeled elements from the many delays a real cycle can contain.
Total modeled time = [(cut length + approach) × passes ÷ cutting feed] + [rapid distance × passes ÷ rapid rate] + tool-change allowance
Machining time from distance and feed
When every pass follows the same path, multiply the cutting and return distances by the pass count. Keep rapid moves separate because they use a different rate. Convert tool-change seconds to minutes before adding them.
Worked milling example
A contour has 100 mm of cutting length, 5 mm of approach, two passes, 50 mm of rapid travel per pass, a 500 mm/min cutting feed, a 5,000 mm/min rapid rate, and one eight-second tool change.
- Cutting time:
(100 + 5) × 2 ÷ 500 = 0.42 min. - Rapid time:
50 × 2 ÷ 5,000 = 0.02 min. - Tool change:
8 ÷ 60 = 0.133 min. - Total modeled time:
0.42 + 0.02 + 0.133 = 0.573 min, or 34.4 seconds.
Theoretical output is 60 ÷ 0.573 = 104.7 parts/hour before loading, inspection, queueing, and other unmodeled time.
Drilling-time form
For a single drilling stroke, use effective axial travel divided by penetration feed: t = L ÷ (fn × RPM). Effective travel can include drill-point allowance, breakthrough, approach, and retract strategy. Multiply by the number of holes only when each follows the same motion and allowance.
Why a feed-time estimate is not a complete cycle time
Commanded feed is not always achieved on short segments. Acceleration, jerk limits, control look-ahead, small arcs, and direction changes can increase time. A full production cycle can also include spindle acceleration, coolant delay, probing, tool measurement, orientation, dwell, pallet exchange, loading, deburring, inspection, and operator response.
- Use CAM or control simulation when motion dynamics matter.
- Compare the estimate with observed cycle history on similar work.
- Keep cutting, rapid, tool-change, and handling allowances as separate inputs.
- Do not quote machine utilization from theoretical feed time alone.
Technical references
Published and formula-checked by MfgWorkbench. Last reviewed September 15, 2026. See our editorial method.