Inventory & Operations
Lead Time Calculator
Turn a supplier lead time into a delivery plan, or work backward from a need-by date to find when to order. Separate production, shipping, receiving and a planning buffer, then see when each stage ends.
Your order timeline
Planning, made visibleSee the whole journey
One date, with every stage behind it.
Break down the wait, keep calendar conventions consistent and copy a plan you can check with your supplier.
The method
Build a lead-time plan from the stages you know
This calculator treats the order as a sequence: supplier or production work, transit, receiving or inspection, then a planning buffer. It moves forward from the order date for a delivery estimate, or backward from the required date for an order-by estimate. Every stage uses the same calendar. Calendar days include weekends; working days count Monday through Friday and any enabled closure rules. The starting date is excluded from each movement. If a required date is closed in working-day mode, the plan finishes on the previous eligible workday.
Example 1
The same order, two different calendars
An order starts Monday, September 28, 2026. Five supplier days, three shipping days, one receiving day and two buffer days total 11 counted days. Calendar mode finishes Friday, October 9. Monday–Friday mode without holiday exclusions finishes Tuesday, October 13: supplier work ends October 5, shipping October 8, receiving October 9 and the buffer October 13. If observed US federal holidays are excluded, October 12 is closed and the finish moves to October 14.
- Start
- Sep 28, 2026
- Stages
- 5 + 3 + 1 + 2 days
- Calendar finish
- Oct 9, 2026
- Working finish, no holidays
- Oct 13, 2026
Example 2
An order-by date for a Sunday deadline
You need an order by Sunday, October 11, 2026, and require two working days. Under a Monday–Friday calendar without holidays, the eligible finish is Friday, October 9. Counting backward two working days gives Wednesday, October 7 as the order date. The result explicitly shows the adjustment rather than silently treating Sunday as a working day.
- Required date
- Sun, Oct 11
- Eligible finish
- Fri, Oct 9
- Duration
- 2 working days
- Order by
- Wed, Oct 7
Before you calculate
Assumptions & limits
- Stages are sequential and do not overlap. If manufacturing and shipping overlap, or suppliers work on different calendars, this simple sum is not a project scheduling model.
- Durations are whole days from 0 to 366, with a combined total from 1 to 366. Enter zero for stages not included in your quote. Dates and results must fall between 2024 and 2035.
- Calendar mode includes every date. Working mode uses Monday–Friday; observed US federal holidays are optional and off by default. Up to 50 custom closure dates can be entered. Duplicate exclusions count once.
- The federal option does not automatically cover state, local, employer, foreign or one-off closures. Confirm your supplier and carrier calendars. Calendar mode ignores closure settings.
- There are no time-of-day cutoffs, transit guarantees, shipping-speed multipliers or inferred holiday policies. The buffer is a duration you supply, not a statistically calculated service level.
- Dates remain in this browser session unless you deliberately copy or download the text plan. No calculation payload is sent, saved or included in the URL.
Keep in mind
Common mix-ups
What is lead time?
For this planner, lead time runs from placing an order to the point when the goods are ready under the stages you entered. Supplier production time alone may omit shipping and receiving, so check what a quoted duration includes before adding another stage.
Does a week mean five or seven days?
A calendar week is seven days. A Monday–Friday working week has five eligible weekdays before holiday exclusions. Convert a quote to the basis the supplier uses; do not treat five working days as five calendar days.
Is the order date counted as day one?
No. Counting begins after the order date. A one-working-day stage starting Friday ordinarily finishes Monday. A zero-day stage leaves the date unchanged.
Can shipping and production use different calendars?
Not in this model. Every stage uses the same selected calendar. If a carrier moves goods every day but a factory works weekdays only, use a separate schedule that models both calendars rather than assuming this result is exact.
How does lead time connect to reorder point?
A reorder-point model estimates the stock needed while waiting for replenishment. Use a demand rate and lead-time duration measured on a consistent basis. An elapsed calendar duration should not be paired blindly with a working-day demand rate.
Sources & calculation notes
Industry reference for ordering, delivery and receipt activities. The four-stage planning convention here is a stated BiznTools model, not a certified ASCM implementation.
Reference for moving dates by working days with weekend and holiday exclusions. This tool uses its own bounded date calculation.
Official federal schedules and observed dates for the optional holiday calendar; not every supplier or carrier follows them.
Calculation and input rules checked: . Engineering validation; no professional accounting review is claimed.