Mastering Project Dependencies With Lead Time

Project dependencies can be a real headache, but there are ways to mitigate the pain.

By understanding lead time, you can better schedule your projects and avoid those last-minute scrambles.

In case you didn’t know we offer in-person and online classes for all levels of Project user.

What Is Lead Time For A Dependency?

Lead time is the amount of time between when a project is requested and when it’s available.

It includes both the time it takes to complete the project, and the time it takes to get approval.

It’s important to understand lead time because it affects how you schedule two tasks.

A dependency with a zero lead time means that the projects are always in sync.

For example, if you have a project that’s always ready to go and doesn’t depend on other projects, its lead time is zero.

It’s a critical path for calculating safety stock inventories, and correct reorder point formula.

It aids the firm in forecasting sales, organizing operations effectively, and increasing client satisfaction.

A financial method that can help an organisation to work out the financial implications of a project rather than time, is a Cost Benefit Analysis.

How To Add Lead Time To A Dependency – Simple Example

Start by creating a simple Microsoft Project plan with just three tasks.

Task 1: Content Writing

Task 2: Copywriting

Task 3: Web Development

Image of the inital tasks

Enter task information, duration, start date and finish date, and predecessors fields of dependent tasks.

Image of the tasks with dates added

Initially, the second and third tasks rely on the first task based on Finish-to-Start logic.

Showing the predecessors changing the dates

How To Add Lead Time To A Dependency – Complex Example

Let’s suppose we want to add lead or lag time to our second dependency (Task 3) so that it doesn’t start for fifteen days after the prior task completes.

Image of the more complicated predecessors formula


1- Go to Microsoft Project

2- Click on the predecessors tab

3- Now, change the logic. Use 1FS+15d

Shows how the dates have changed based on the formula

What is 1FS+15d?

It denotes a Finish-to-Start dependency (or “FS”) where the task is dependent on task “1” and is delayed by fifteen days of lead time.

Predecessor Syntax – Explained

It’s crucial to remember the following rules while adding lead and lag time to a predecessor.

The sequence of the predecessor syntax should be in the following order:

    • Predecessor task ID
    • Dependency relationships
    • Operator
    • Lag time
    • Lag unit

[Task ID ] [Dependency Type] ([Operator] [Lag Time] [Lag Units])

1 FS + 15 d i.e 1FS + 15d

Task ID is the row number of the Microsoft Project plan. If you want task 2 and task 3 to depend on task 1, Simply put “1” in the syntax.

The dependency relationships are of four types:

    • FS: Finish-to-Start
    • SS: Start-to-Start
    • SF: Start-to-Finish
    • SS: Start-to-Start

Depending on whether you want to create a positive or negative lead time, the operator can be a plus (+) or minus (-) sign.

A plus symbol indicates that you’d like to postpone the start of a task for a specific number of days after another task has been completed.

A minus sign, on the other hand, implies that you’d want the successor task to begin a few days before the preceding one ends.

The number of days, hours, weeks, or whatever period you want to calculate in the lag is known as Lag Time.

The lag is defined by the Lag Time, which has a number of subdivisions called Lag Units. There are five distinct Lag Units. i.e

    • d: Days
    • w: Weeks
    • mo: Months
    • h: Hours
    • m: Minutes

You can use capital or small letters for lag units as they have the same meaning for the Microsoft project.

If you want to look at a project as a list of tasks cascading down based on their predecessors, why not implement a Waterfall Methodology in Project?

Team working on laptops in office

Lead Time Use Cases

When you add lead time to successor tasks, the activity on that task overlaps work of the previous one.

  • Supply chain planning uses the lead time to calculate the number of days it takes to make or obtain an item that will be used to produce a finished good. A gantt chart is then formulated to inspect the supply chain planning and management.
  • Inventory management: In inventory management, the time between when an order is placed to replenish inventory and when it is received is known as lead time. The amount of stock a firm must maintain at any moment is determined by lead time.

Lead time is just one of Project’s many advantages, read our full guide to Microsoft Project’s Pros and Cons here!

Troubleshooting Lead Times

If you’re facing issues calculating lead time, then check the following tips:

1. Syntax Sequence

If the sequence of the syntax is incorrect, then the Microsoft project is not going to show you desired results.

Correct Sequence[Task ID ] [Dependency Type] ([Operator] [Lag Time] [Lag Units])

2. Task ID

Check your task ID. Task ID in syntax should be correct as it defines the task depending on the first task.

3. Dependency

Choose the right dependency relationship to operate the syntax accordingly.

If you don’t add any dependency type, Microsoft Project Plan will consider default settings as “FS” or Finish to start dependency.

With lead or lag time: If you want to add lead or lag time, you have to use operator, lead or lag time, and lead or lag unit.

Without Lead or lag time: If you don’t want to add lead or lag time, then enter predecessor task ID and dependency type.

4. Lead Time and Lead Unit

Check the distinction between minutes (m) and months (mo). If you have entered the wrong lag unit, it will trouble you.

Keep in mind that lag is calculated based on working time. As a result, fifteen days is not 15 calendar days; it’s 15 working days.


Tracking lead time and employing it correctly can be a powerful predictor of how quickly work will get done, allowing you to predict delivery dates.

You should track lead time in order to improve the flow of your project.

This is especially important if you are working with others who are not able to see the big picture and need to be kept in sync.

Looking for more Microsoft Project guides, read here on how to create a Kanban Board!


About Ben Richardson

Ben is a director of Acuity Training which he has been running for over 10 years.

He is a Natural Sciences graduate from the University of Cambridge and a qualified accountant with the ICAEW.

He previously worked as a venture capitalist and banker and so had extensive experience with Excel from building financial models before moving to learn SQL, Microsoft Power BI and other technologies more recently.