M3 Manufacturing Lead Time Calculator
Planning lead time is only as good as the numbers behind it. This calculator builds the lead time from its parts and separates the fixed part from the part that grows with order quantity, which is the split most planning engines expect.
Your numbers
Planned efficiency or OEE-like factor applied to setup and run.
Your results
Single-operation estimate. Multi-operation routings with overlap or parallel paths need the longest path summed per operation.
Lead time vs order quantity
Sweeps Order quantity from 1 to 500, holding your other inputs fixed.
Compare planned vs actual lead times
Optional: analyse how real order durations differ from planning data in your M3 system.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the lot size, setup hours, run minutes per piece and the efficiency you plan for. Add queue time before the operation and any move or wait time after. The calculator converts everything into calendar-free working days using the hours per day you supply, then adds queue and move time. Run it once per operation and add the results for a straight-through routing, or take the longest path if operations overlap.
- Use realistic efficiency, not the standard rate
- Queue time is usually the biggest lever
- Match hours per day to the shift pattern
- Check the result against recent actual order durations
The method
Work hours equal setup plus run, divided by efficiency. Divide by available hours per day to get processing days. Total lead time is processing days plus queue and move time. The fixed lead time is everything that does not change with quantity, and the variable part is run time per piece converted to days. Planners often load these as separate fixed and variable lead time fields, so the split is what you carry into planning data.
Reading the chart
The lower line is the fixed portion and the upper line is the total. The gap between them widens as the lot grows. If the lines nearly touch at normal lot sizes, lead time is dominated by queue and setup, and reducing batch size will not help much. If they diverge sharply, run time dominates and splitting the order across machines may shorten the lead time.
- High fixed share points to queue and setup problems
- High variable share points to capacity or routing design
- Compare against actual order dates before changing master data
Common mistakes
Using standard run rates without an efficiency factor produces lead times that are always optimistic. Another common mistake is double counting queue time in both the routing and the item lead time. Finally, mixing calendar days and working days will distort the result, so keep one convention and make sure the calendar used in planning matches it.
Frequently Asked Questions
What is the difference between fixed and variable lead time?
Fixed lead time is incurred per order regardless of size, such as queue, move and setup. Variable lead time grows with quantity, such as run time per piece. Splitting them lets planning scale lead time correctly for small and large lots.
Should efficiency be applied to setup as well?
Usually yes, because setups also overrun in practice. If your setup times are already realistic actuals, set efficiency based on run time only by adjusting inputs, or accept a slightly longer estimate.
How do I handle several operations?
Calculate each operation separately and add the processing and wait times in sequence. If operations overlap, use the overlap rule you actually run on the shop floor and apply it to the sum.
Can I use this for purchased items?
Not directly. For purchased items, lead time is supplier lead time plus transit and receiving. The safety stock calculator in this set handles lead time variability for those items.
If you want actual order durations compared with planned lead times across your M3 routings, Netray can run that analysis on your data, read-only.
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