Lead Time Calculator
Total lead time from order to delivery, built from its parts — processing, procurement, production, queueing and shipping — and how much of it is actually work.
Lead time is the sum of every stage an order passes through, and in most operations the parts are dominated by waiting: a job that takes six hours of work sits in queues for six days.
How the lead time calculator works
Lead time is the sum of every stage an order passes through, and in most operations the parts are dominated by waiting: a job that takes six hours of work sits in queues for six days. The share that is genuine work is the process efficiency, and single digits are common.
The lever is almost never speeding up the work. It is removing the waiting, which is what every lean improvement is actually doing.
Formula: lead time = Σ stage days; efficiency = work days / lead time
Worked examples
| Inputs | Total lead time (days) | Note |
|---|---|---|
| A typical make-to-order flow | 18.5 | 18.5 days, 16% work |
| Stock on hand | 11.5 | a week shorter |
| A tight promize | 18.5 | over by more than a week |
FAQFrequently asked questions
What is lead time?
The elapsed time from order to delivery — every stage, including the waiting. It is what the customer experiences and what stock has to cover.
What is process efficiency?
The share of lead time that is actual work. Under 10% is normal and shocking; it says most of the time an order spends is in a queue.
How do I reduce lead time?
Attack the waiting, not the work. Smaller batches, fewer handoffs and stock of long-lead materials remove days; speeding up a two-day production step saves hours.
Why does the promize matter?
Because a promize the process cannot meet is met by expediting, which costs more than the lead time it saves and disrupts every other order.
Is shipping part of lead time?
To the customer, yes. Measure what they experience, from the moment they order to the moment they have it.
Where these figures come from
- Nakajima (1988) — Introduction to TPM — the origin of Overall Equipment Effectiveness and its six big losses
- OSHA — the US workplace safety administration
Last checked: September 2026. Definitions follow standard operations-management practice; where plants commonly differ, the page says so.