Home / Calculators / Lead time calculator
Inventory and ordering
Lead time calculator: from order to usable stock
Enter the days each stage takes, from your own approval to the moment stock is ready to use. You get total lead time, a planning figure with a buffer, and a weeks view.
Total lead time is the sum of every stage between deciding to order and being able to use the stock. At the default numbers it is 38 days, or 44 days once you add a 15 percent buffer.
Written by Procurement VMS Editorial Team · Reviewed by Michael, Procurement Advisor Expert · Updated
Your numbers
The boxes start with an example so you can see how it works. Replace them with your own figures.
Your result
Plan with 44 days, not the 38 days on paper. Order that far ahead of the day you need the stock to be usable.
| Total lead time | 38 days |
|---|---|
| Planning lead time with buffer | 44 days |
| Planning lead time in weeks | 6.2 weeks |
| Share spent at the supplier | 39% |
The currency box changes the label only. Enter amounts in the currency you choose.
Free PDF and Excel
Save this result as a PDF guide and an Excel model
Free to download. You enter your name, work email and phone number, and the files are ready at once.
- PDF guide with the formula, a worked example and a checklist of what to enter
- Excel model with live formulas, so your own numbers recalculate at once
- Ready at once after the form, with no account to create
The files open with the example numbers from the page. Type yours over the blue cells in the Excel file. The calculator on this page is free to use without a form.
How the lead time calculator works
The formula
Total lead time = approval + supplier time + transit + customs + receiving. Planning lead time = total x (1 + buffer %).
Lead time looks like one number but it is a chain of stages, and each stage has its own owner. Splitting it shows where the days go, and where a fix is cheap. Internal approval is often the stage you control most.
Use observed times, not the quote. Pull the last ten orders, measure each stage, and use the averages. The buffer then covers the orders that run late.
The example numbers are illustrative and are not benchmarks. Use your own data for any decision.
How to use it with your own data
- Fill in each stage with an average from recent orders.
- Set the buffer from how often deliveries arrive late, not from a fixed rule.
- Use the planning figure in the reorder point calculator so the trigger matches how the supplier really performs.
Mistakes that skew the answer
Counting from the supplier confirmation
The clock starts when you decide to buy. Your own approval days count.
Forgetting receiving time
Stock on the dock is not stock you can use. Inspection and put-away take days.
Using the best delivery on record
Averages and a buffer give a plan you can keep. A single fast order sets you up to miss.
What to do with the result
If approval takes more than a few days, review the route in your purchase requisition process. If transit is the long leg, compare freight options with the freight cost per unit calculator.
Questions about the lead time calculator
What is the difference between lead time and delivery time?
Delivery time is the transit leg. Lead time runs from the decision to order through to usable stock.
How do I measure supplier lead time?
Record the order date and the date goods are booked in for the last 10 or more orders, then average the gaps.
Should I plan with the average or the longest lead time?
Plan with the average plus a buffer, and cover the remaining variation with safety stock.
Does lead time include weekends?
Count calendar days unless your supplier works to a business day calendar. Be consistent with the unit you use for daily demand.