Lead Time Quote Calculator (Customer Order Promise)
Customer service is asked for a delivery date before planning has run a schedule. This calculator turns the pieces of lead time into a defensible quote, with the waiting time made visible instead of guessed.
Your numbers
Good units per hour at the bottleneck operation.
Hours per day the work center runs, e.g. 7 x 2 shifts.
Load ahead of this job at the bottleneck.
Zero if stock is on hand.
Plating, heat treat, anodize and the like.
Your results
Planning estimate only. It assumes one bottleneck and that material wait and queue overlap. Replace inputs with your routing and actual load.
Quoted work days vs order quantity
Sweeps Order quantity from 50 to 3000, holding your other inputs fixed.
Quote from live capacity data
Optional: we can review how routing and load data in your ERP could feed quoted lead times.
Optional. The tool and every export work without this. No spam.
How to use the calculator
Enter the order quantity, the run rate and setup time at the bottleneck operation, and how many hours your work center runs each day. Add the hours already queued ahead of the job, any material wait, outside processing and transit. Set a buffer and read the quoted lead time in work days and calendar weeks. Use the chart to see how quantity pushes the date out and test what a smaller first shipment would do.
- Get the queue hours from the shop floor load report, not memory
- Use net good units per hour, not rated speed
- Set material days to zero only if stock is physically available
- Increase the buffer when the shop has unstable machines or suppliers
The method behind the number
Lead time is mostly waiting, not processing. This calculator sums wait before start, process time, outside process time and transit. Material wait and queue run in parallel, so the longer governs: max(material, queue). Process days equal (setup + run hours) divided by productive hours per day. The buffer then scales the total to cover variability. The result is rounded up because customers hear a date, not a decimal.
Worked example
500 units at 20 per hour is 25 run hours, plus 3 setup hours, over 14 hours a day is about 2 days. Queue is 96 hours, or about 7 days, which is shorter than the 10-day material wait, so material governs the start. Add 2 process, 5 outside and 3 transit days for 20 work days, then a 15% buffer gives 23 work days, roughly 5 calendar weeks on a five-day week.
Common mistakes
The usual errors are quoting from process time alone and ignoring the queue, adding material and queue instead of overlapping them, and giving the same buffer to every job regardless of risk. Another is promising from the quote date when the real clock starts at PO plus approved drawings. Review actual versus quoted lead times monthly and tune the buffer.
Frequently Asked Questions
How do you calculate lead time for a customer quote?
Add the wait before start, the process time at each operation, any outside processing and transit. Overlap material wait with queue time rather than adding them, then add a buffer for variability. Round up to a date the customer can plan around.
How big should the safety buffer be?
It depends on how predictable your shop is. Stable, repeat work may need 5 to 10 percent. New parts, outside processes or constrained machines often justify 20 percent or more. Compare quoted to actual delivery and adjust.
Why does lead time grow so quickly with load?
As utilization approaches full capacity, queue time rises faster than linearly. A bottleneck at 95 percent load has a much longer queue than one at 80 percent. Check queue hours before quoting during busy periods.
Should I quote from order date or from receipt of drawings?
State the clock start explicitly, usually receipt of a clean PO and approved drawings or specs. Starting from the quote date commits you to dates you cannot control if the customer is slow to confirm.
If quoted lead times are guesses today, Netray can help connect this logic to live ERP routings, work center load and supplier lead times, with the plan staying read-only.
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