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Leads, Lags & Float – Understand the Difference through Tutorial

Last updated on 24th Aug 2022, Blog, Tutorials

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Kiran Malik (Associate Product Manager )

Kiran Malik is an associate product manager with four years of experience in ITIL, Prince2, Google Go, BizTalk, and CyberArk. He has expertise in affiliate, pacesetting, authoritative, coercive, and laissez-faire management styles.

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When it comes to project activity management, activity sequencing is one of the major tasks.

Among many other parameters, float is one of the key concepts used in the project scheduling.

Floats can be used to facilitate freedom for a specific task.


There are 4 parameters for each related to the timelines. Are:

Earliest start time (ES) – Earliest time, an activity can start once the previous dependent activities are over.

Earliest finish time (EF) – This would be ES + activity duration.

Latest finish time (LF) – The latest time an activity can complete without delaying the project.

Latest start time (LS) – This would be LF – an activity duration.

The float time for an activity is the time between the earliest (ES) and latest (LS) start time or between earliest (EF) and latest (LF) finish times.

During the float time, an activity can be delayed without delaying the project complete date.

Leads and Lags

Leads and Lags square measure kinds of float.

Associate in Nursing example to know this.

In project management, there square measure four kinds of dependencies:

end to begin (FS) – task doesn’t begin till the previous task is finished

end to complete (FF) – task doesn’t end till the previous task is finished

begin to begin (SS) –task doesn’t begin till the previous task starts

begin to complete (SF) – task doesn’t end before previous task starts

Take the situation of building a pair of identical walls of constant house mistreatment constant material.

Building the primary wall is task A and building the second is task B.

The engineer must delay task B for 2 days.

This occurs as a results of the usage of bran-new materials in each A and B.

Therefore, the engineer should initial learn from A and so, if applicable, apply to B.

As a result, there’s Associate in Nursing SS link between tasks A and B.

The time between the beginning dates of the 2 tasks are often explained as a lag (2 days during this case).

If the relationship between task A and B was Finish to Start (FS), the ‘lead’ can be illustrated as:

Task B started prior to Task A with a ‘lead.’

Schedule Network Diagram, PDM & vital Path

1. Schedule Network Diagram –It is a graphical illustration of logical relationships among the project activities. Dependencies among those project activities.

These dependencies mirror the order during which to schedule project activities.

Activity may be either forerunner or successor admire a dependent activity :

forerunner –An activity that logically comes before a dependent activity within the schedule

Successor – A dependent activity that logically comes when another activity on the schedule.

2. PDM (Precedence schematization Method) –

PDM is one among the Schedule Network Diagrams or schedule models during this model, nodes represent the activities.

One or a lot of logical relationships link these nodes diagrammatically to show the sequence to perform these activities.

Assign precedence relationships supported the dependencies between each activity.

PDM has four sorts of precedence relationships to end the network diagram – metallic element, EF, and LS & LF.

3. vital Path –

In a PDM, a vital path could be a tool to seek out minimum project length.

it’s the sequence of activities to represent the longest path through the project.

This longest path finds the shortest attainable project length.

All activities on the vital path referred to as the vital path activities.

What is Float in Project Management?

Types Of Float Management

In project management, float, typically additionally said as “slack,” could be a range that denotes the quantity of your time a task may be delayed while not impacting subsequent tasks or the project’s overall end.

It’s vital to trace once maintaining a project schedule.

There ar a pair of sorts of float in project management, free float (FF) and total float (TF).

Free float – The quantity of your time that a task may be delayed while not the impacting of subsequent tasks.

Total float – The quantity of your time a task or a project may be delayed while not impacting the project finished time.

How To Calculate Float

There ar few alternative ways to calculate float.

The technical calculations that ar a part of the vital path technique are going to be confusing if they’re not up to hurry on CPM and network diagrams.therefore outline the way to do these calculations in layman’s terms.

It’s vital to notice that almost all project managers don’t even do float calculations by hand as a result of it’d be long, to not mention the project set up is often dynamical.

The best thanks to get float numbers and different valuable calculations in period is to use skilled project management software package .That mechanically will the amount crunching.

ProjectManager’s Gantt charts, dashboards and project reports can mechanically value everything required to trace float, slippage, vital methods and a lot of.

Total Float Calculation

Total float will apply to the project as a full, or to one task.

A project’s total float is that the distinction between the end date of the last task on the vital path and also the project end date.This tells what proportion total time the vital tasks may be delayed before the complete project misses its completion target.To calculate a task’s total float, take the distinction between the end date of the last task on the vital path and also the planned end date of the task.

A simple formula to calculate total float or slack is our usual formula:

i.e. LS (Late Start) – metallic element (Early Start) or LF (Late Finish) – EF (Early Finish)

Free Float Calculation

A free float could be a range that shows however long a particular task may be delayed before it impacts following sequent task.Therefore, to calculate the free float of a task, simply take the distinction between following task’s planned begin date, and also the current task’s finish date.

An Example of Float

Let’s assume we have a tendency to ar building a brand new room, and have ninety days to end the method as a result of I even have an enormous party planned in three as to complete the room renovation project, the subsequent things happen in order:

  • Drywall installation
  • Cabinet installation
  • Plumbing/Electric
  • Floor installation

These activities created up the vital path and have zero float.

Then there ar further tasks like painting and decorating that need to happen, however they need a lot of flexibility on after they may be done. These tasks created up the non-critical path.

Painting may be done any time when the drywall is put in, therefore it’s a lot of float.

Decorating may be done any time when the painting is finished, therefore decorating has some float additionally.

Why Float Matters

Float is simply a technical range utilized in the network diagrams. however it’s truly a additional powerful tool that may facilitate groups learn additional regarding their work and facilitate increase the productivity of comes. It Keeps comes heading in the right direction.To start, screening a project’s total float (TF) is crucial to making sure that the general project goes to be delivered on time.If you notice that a project’s TF is obtaining on the point of zero, it’s currently crunch time to create certain the ultimate remaining tasks square measure completed expeditiously.

Requirement to feature further resources to assist the project team end the ultimate tasks quicker than originally planned.

If the project isn’t getting to end on time.Then it’s time to own a talk with the shopper or stakeholders to allow them to understand that they ought to expect a delay.It Improves PrioritizationFree float (FF) is additionally a useful range to a result of it offers how to come to a decision that tasks have to be compelled to be prioritized and which may be pushed back to a later date.

If a task has zero float or a coffee float range, then it ought to visit the highest of the priority list that the project team will knock it out.Conversely, any tasks with additional FF numbers may be pushed to all-time low of the priority list.

Because there’s no rush to induce them completed.It Boosts Team Morale.Finally, free float may be accustomed facilitate to stay varied project groups happy and economical.

Task A is moving towards a really low free float range, which means it’s in danger of delaying task B. during this case, will provide the team functioning on Task A some further resources to assist them complete their work. Could conjointly let the team United Nations agency are functioning on task B understand that they ought to brace oneself for a delay within the work.By watching FF, we will catch problems early and ensure that groups don’t get annoyed by unexpected delays.If team B is aware of to expect delays, they’ll fill the time by functioning on one thing else.

Benefits of float in project management

Can imagine, project float — typically known as project “slack” — is additional useful for project managers, notably people who administrate giant, sophisticated comes with multiple task ways.

Of course, project float helps staggeringly with resource management, scheduling, and keeping comes on trace for a timely delivery.But float is additionally extraordinarily valuable for PMs operating with contractors and therefore the internal resource managers. For example, by knowing exactly what quantity free float and total float a selected task has, provide the contractors additional leeway to figure withThis implies they’ll realize the schedule by selecting the most effective crew for the work, operating as materials arrive, operating within the best climate, and avoiding overtime.

What is the difference between total float and free float?

    Total Float Free Float
    Evaluate at path level of activities Evaluate at the activity level
    Explains flexibility of a path w.r.t project end date Explains flexibility of activity w.r.t its successor start
    Total Float Formula LS-ES or LF-EF Free Float Formula ES (of successors) – EF of current activity -1
    Can come into existence if the network diagram has more paths and there are activities that are not on the Critical Path Can come into existence if the successor is having more than one activity converging on it .


For a project manager, the concepts of float, lead and lag made a lot of sense and sense.

These aspects of tasks are most important in order to calculate project timeline variations and eventually the project finish time.

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