Lead and lag are the terms used to define a relationship between the tasks on a project. Both are scheduling terms used with relationships like Finish to Start, Start to Start. We will see below simple examples.
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Lead
A Lead is the amount of time that successor activity is ahead of its predecessor activity. For example, in a construction project, it is maybe desired to start working on landscaping four weeks before the furniture purchase. This will be shown on a scheduling diagram like below.
This type of interlinked activity sequence is known as the finish to start and is the most often used type of sequence in project scheduling. In simple words, we can say that the lead time is four weeks.
This type of interlinked activity sequence is known as the finish to start and is the most often used type of sequence in project scheduling. In simple words, we can say that the lead time is 4 weeks.
In this scenario, these 5 days’ t be before the design finishes when the development starts are called lead time.
Example for Lead
Let’s take the example of a project involving software development. We might want to start with the programming of the hardware screen where the software will run as the programming itself is dependent on technical design, including the dimensions of the screen. So both activities can definitely not start simultaneously. When we go deep into the activity plan, we know that technical design will take 20 days, but after 15 days, most activities are in the final stages. Most importantly, the information required for programming is concluded so we can start programming from thereon. Hence the overall duration of a project will be reduced.
Lag
Opposite to Lead, Lag is the amount of time successor activity is delayed from its predecessor activity.
For example, the time duration for the first activity is 2 days, and then there is a gap of 3 days before you start the next activity, so you can say that there is a lag of 3 days. It will be shown on the scheduling diagram as Finish to Start.
Let us look at the below snip, here we have to wait to start Paintwork after Plastering is finished. This wait is mandatory as Platser will take time to set or cure.
Similarly, we can also have a case like you may start editing a book after 10 days you begin writing it. It will be shown as a start-to-start sequence as below.
Similarly, we can also have a case like you may start editing a book after 10 days you begin writing it. It will be shown as a start-to-start sequence as below.
Example for Lag
Let’s consider another example from a construction project. It is only logical to first prepare concrete and gets the foundation work completed. Only then can we start working on the rest of the construction activities. But there is one problem, as the foundation requires curing concrete for at least 3 days, the remaining work can’t be initiated. These 3 days’ time can be termed as lag, which can’t be avoided. So it is important to understand the logical dependencies of activities for precise project planning.
Wrap Up
Lead and lag both are important concepts and must be considered in project schedule development. Lead is the amount of time that successor activity is ahead of its predecessor activity. Whereas Lag is the amount of time successor activity is delayed from its predecessor activity.
Great post! I completely agree that understanding the difference between lead and lag indicators is crucial for effective project management. As a project manager myself, I’ve found that using lead indicators to anticipate potential issues and lag indicators to measure progress can greatly improve our ability to steer projects towards success. Thanks for sharing this valuable information!
Great post! I really appreciate the clear explanations and the simple examples you provided. It’s often confusing to distinguish between lead and lag in project management, but your breakdown made it much easier to understand. Thanks for sharing!