I have a task within my project criteria which states: "Purchasing lead-time for the steelwork is estimated at 60-80 days".

What does lead time mean? Do I have to make special considerations for this?

  • 4
    What research have you done? A quick Google search brings up a definition, a link to a Wikipedia page, and other resources. What don't you understand about these? What additional clarification do you need?
    – Thomas Owens
    Dec 17, 2014 at 17:24

3 Answers 3


Lead time is the delay between the initiation and execution of a process. For example, the lead time between the placement of an order and delivery of a new car from a manufacturer may be anywhere from 2 weeks to 6 months.

According to the Business Dictionary, Purchasing lead-time is the, "Interval between a decision to purchase an item and its receipt at the warehouse or stores. It is the total of order preparation time, order release time, supplier lead time, shipping or transit time, and receiving, inspection, and put-away time."

Yes, you do have to give special consideration for this. You must factor this lead time in your plan. More importantly, you must note that the Purchasing lead-time doesn't include time to create the design and specification for the steelwork, time to locate and qualify vendors, get quotations and conduct negotiations and make a decision. You should make sure that these tasks are properly incorporated in the plan and time estimates are accounted for.


As a note, lead time in Microsoft Project is expressed as a negative value in the lag field on a predecessor/successor relationship. So if you had a two tasks:

  • Task 1: Purchase Steel
  • Task 2: Erect Steel Structure

the link relationship for Task 2 would be 1FS+80days.

  • Hi, Julie. I don't know enough about MS Project to vote on your answer, but I wanted to note that yours is currently the only answer that addresses the technical side of how to represent lead time in MS Project.
    – Todd A. Jacobs
    Dec 17, 2014 at 20:36
  • Julie's code would put Task 2 before Task 1. The dependency is FS+80, which will push task 2 out 80 days. Another solution is to insert another package with no resources that represent the wait time, such that you have no leads or lags, which I understand hoses up the critical path calculations in project. Dec 17, 2014 at 20:57
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    Sorry David, you are correct. My train wasn't engaged fully. I'm not aware of any issue with lead or lag time causing issues with critical path calculation. If the lead or lag is in elapsed duration (edays, eweeks) that can cause issues when the lead or lag would cause the successor to be scheduled during non-working time.
    – JulieS
    Dec 18, 2014 at 15:12
  • I was just told this recently. I did a bit of research and it is one of the criteria for schedule health, i.e., minimized leads and lags in the logic. Was told the algorithm can't cope with it and produces a critical path with validity issues. But I don't know for sure; I still use them. Dec 18, 2014 at 15:20
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    Lead/lag versus tasks without resources has been a topic of discussion for quite some time. In Project 2013 a non-milestone task without assignments will be flagged in the "Best Practices" report, while others dislike lead and lag. I still prefer lead/lag over tasks without assignments. Both require some sort of explanation in the schedule so others understand.
    – JulieS
    Dec 18, 2014 at 15:25

Ashok gives a great definition for Purchasing lead-time.

Because the term lead time, is a catch-all for a whole load of preceding tasks, its even more important to check how the estimate for its duration came about. A special consideration for you would be to check a little more rigoriously how the estimate has come about. Some questions you may want to consider are:-

  1. In previous projects has purchasing steelwork always taken 60-80 days, is this estimate still valid today?
  2. Are there any circumstances that mean the purchasing for this project will be different and could that effect this estimate?
  3. Why 60 to 80 day, what happens during that time and why the 20 day variance, is that contingency?

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