Lead Time Calculator
Calculate Lead Time step by step: Lead time = delivery date − request date (when the customer asked).
In short
Formula: Lead time = delivery date − request date (when the customer asked). Shown as average, median and 85th percentile.
What this calculator does
Calculate Lead Time step by step: Lead time = delivery date − request date (when the customer asked). Worked example, questions and limitations included.
Use it to turn Lead time — item 1, Item 2, Item 3, Item 4 (optional), and the other shown inputs into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this agile delivery calculation.
Inputs and what they mean
- Lead time — item 1
- — number value.
- Item 2
- — number value.
- Item 3
- — number value.
- Item 4 (optional)
- — number value.
- Item 5 (optional)
- — number value.
- Item 6 (optional)
- — number value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
Lead time comes from Lean: the time the customer waits, from request to delivery. It includes queue time before work starts, so it is always at least the cycle time.
Little's Law (J. D. C. Little, 1961): average WIP = average throughput × average cycle time, valid for a stable system over the same period.
Flow times are skewed; the median and 85th percentile are more useful for forecasts than the average.
Lead time = delivery date − request date (when the customer asked). Shown as average, median and 85th percentile.
Inputs used: Lead time — item 1, Item 2, Item 3, Item 4 (optional), Item 5 (optional), Item 6 (optional).
Worked example
Five requests
- Average = 65 ÷ 5 = 13 days.
- Median = 12 days; 85th percentile = 20 days.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- Up to six items; use a spreadsheet for larger samples.
- Nearest-rank percentile is coarse for small samples.
- Mixing very different item types distorts the figures.
- Results are planning estimates built only from the figures you enter. They are not a guarantee of cost, schedule or delivery, and they do not replace your organisation's own project controls.
- The result depends on the values you enter for this lead time calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Common questions
What is the difference between lead and cycle time?
Lead time starts when the request is made; cycle time starts when work begins. The gap is waiting time in the queue.
Why show the 85th percentile?
It gives a service-level style answer: 85% of items finished within this time. It is a common Kanban forecasting practice.
How many items do I need?
More is better. With only a handful, percentiles are rough; collect at least a few weeks of data.
How do I use the Lead Time Calculator?
Enter the required values for Lead time — item 1, Item 2, Item 3, Item 4 (optional), Item 5 (optional), and the other fields shown. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Lead Time Calculator use?
Lead time = delivery date − request date (when the customer asked). Shown as average, median and 85th percentile. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the Lead Time Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
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