Lead and Lag in Project Management: Definition and How To Use

Lead and Lag functions in SQL Server 2012

What is a lead?

The overlap of scheduled activities is referred to as leads and lead time. When one phase of a project starts before the previous phase has ended, this is known as a lead. In these scenarios, leads exist when the predecessor activity can start without the consideration of any physical constraints. In network diagrams, subtraction symbols represent leads. This is because leads shorten project lengths by overlapping activities.

Project schedule managers need leads because leads give them the ability to spot potential activity overlap and save time. For instance, completing a project with two activities that each take four days and six days would require ten days. The project can now be finished in eight days, though, if you can begin the second activity two days before the first one ends. A project with no lead time and a requirement that each activity be completed before starting another would probably end behind schedule.

What is a lag?

The time that passes before the next activity in a project’s timeline can start is referred to as “lag” in project management. There are many reasons to schedule a lag, including:

Plus signs are used in network diagrams to represent lags because they demonstrate the passage of time. Lag time may refer to hours, days or weeks. Any period of time that must pass between a successor activity and a predecessor activity is known as a lag.

What are lead and lag used for?

To identify necessary delays and prepare for time-saving opportunities, project managers use leads and lags. Understanding lead and lag time when scheduling projects can help managers predict the project’s completion date with accuracy. Additionally, these tools enable them to streamline project phases and cut back on unneeded lag time.

Managers can use leads and lags to make schedules, track productivity, and order events logically within a larger project timeline. Leads and lags can be used by project schedulers, IT specialists, and construction managers to plan, organize, and optimize their projects. Project managers sometimes use network diagrams to accomplish this, where plus symbols denote lags to represent the addition of time required to complete the project and subtraction symbols denote leads to denote the subtraction of time from the total.

Using lead and lag in network diagrams

Network diagrams are used by schedulers, coordinators, and project managers to show the connections between the various project phases. In order to improve your scheduling process, diagrams can be a useful tool for modeling activities and identifying lead and lag times. Network diagrams, also known as the precedence diagramming method, let schedulers examine potential leads and lags to find logical relationships.

There are four categories of logical relationships in a precedence diagram:

Example of lead and lag

Examples of lead and lag in the real world include planning a residential or commercial construction project, sequencing a software development project, or starting an excavation. Here is an illustration to illustrate how lead and lag can affect a project using the construction application:

When starting a project with many moving parts, a contractor might make a list of dependent predecessor activities. They might begin by describing the key stages of their project, such as design, construction, utility installation, and finishing Tasks like creating blueprints, excavation, framing, plumbing, electrical, dry walling, painting, installing windows, and landscaping are listed within those phases. Some of these tasks must be completed before they can start, while others might not.

For instance, the team cannot start dry walling the house until electrical wiring is installed. However, because landscaping and window installation are not related, they can both be done at the same time. In this case, a contractor might indicate relationships by identifying dependencies with tags like FS and SS. Project managers can optimize task start dates and prevent redundancy or unnecessary delays by understanding logical relationships.

The leads and lags can then be represented with plus and minus signs. If painting can start two days after drywall installation, that can be written as FS + 2. The successor activity can’t start until the predecessor activity is finished because there is a two-day lag. Wiring can start on this example project three days after framing does. The electrical only needs to be started; the framing doesn’t need to be finished. A contractor may represent this as SS – 3.


What is lead and lag with examples?

Lag. The successor activity is accelerated in lead, which is only applicable to finish-to-start activity relationships. Lag, which can be found in all activity relationship types, is a delay in the succeeding activity. Only finish-to-start activities—in which A must complete before B can begin—have lead.

What is the difference between lead and lag function?

You enter lead time as a negative value. Lag time is the difference in time between tasks that are dependent on one another. For instance, you can create a finish-to-start dependency and specify a two-day lag time if you need to delay the start of one task by two days before it is completed.

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