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Critical Path Method (CPM) Course

project management

In the quest to become an exceptional project manager, there is no denying that you have a lot to learn. However, you can begin the process towards excellence in this field with one crucial methodology known as the Critical Path Method. If you want to develop the necessary skills for these methodologies, then you are definitely going to want to keep reading.


Introduction to the Critical Path Method (CPM)

If you have been into project management, I’m certain you have effectively heard the term ‘critical path method.’ If you are new to the subject, it is best to begin with comprehension the ‘critical path’ and after that move on to the ‘critical path method.’

Critical way is the consecutive exercises from begin to the finish of an undertaking. Albeit numerous projects have just a single critical path, a few ventures may have in excess of one critical paths depending on the stream rationale utilized as a part of the project.

If there is a deferral in any of the exercises under the critical path, there will be a postponement of the project deliverables.

Critical Path Method

Most of the circumstances, if such postponement is happened, venture quickening or re-sequencing is done in order to accomplish the deadlines. Critical way technique depends on scientific computations and it is utilized for booking project activities. This strategy was first presented in 1950s as a joint wander between Remington Rand Corporation and DuPont Corporation.

The starting critical path technique was utilized for overseeing plant support ventures. In spite of the fact that the original strategy was created for development work, this technique can be utilized for any project where there are reliant activities.

In the critical path technique, the basic exercises of a program or a task are distinguished. These are the exercises that directly affect the consummation date of the project.

What is the Critical Path Method?

In CPM, you construct a model of the undertaking, including every one of the exercises recorded in a work breakdown structure, the term of those assignments, imagine a scenario where any errand conditions there are and separating turning points to demonstrated bigger periods of the task or focuses in which your expectations are expected.

With this data, you figure out what is the way to complete the undertaking with the minimum slack. Essentially, you’re making sense of to what extent the errands that make up the undertaking will take.

Critical Path Method

This technique was produced in the late 1950s by Morgan R. Walker of DuPont and James E. Kelley, Jr., of Remington Rand. DuPont was at that point utilizing a forerunner of CPM as early the 1940s, and it was connected to the Manhattan Project.

The procedure begins with a rundown everything being equal, or a work breakdown structure, the length of each errand, what conditions there are and afterward mapping breakthroughs and deliverables.

When to Utilize the Critical Path Method?

When to Utilize It: CPM works better with littler or moderate sized undertakings. The bigger the task, the more troublesome it can be to take every one of the information you have to outline and understand it without software.

How to Use Critical Path Method?

The 6 Steps in Critical Path Method

Let’s examine how Critical Path strategy is utilized as a part of training. The way toward utilizing basic path method in venture arranging stage has six steps.

Step #1 – Define Activities

You can utilize the Work Breakdown Structure WBS to recognize the exercises associated with the project.

This is the primary contribution for the Critical Path method. In action particular, just the more elevated amount exercises are chosen for Critical Path Method.

When point by point exercises are utilized, the Critical Path strategy may turn out to be excessively unpredictable, making it impossible to manage and maintain.

Step #2 – Sequence Activities

In this progression, the right movement grouping is set up. For that, you have to ask three questions for each assignment of your list:

  • Which errands should occur before this undertaking happens.
  • Some errands ought to be finished in the meantime as this task.
  • Which assignments ought to happen promptly after this task.

Step #3 – Draw the Network Diagram

Once the movement arrangement is accurately recognized, the system graph can be drawn refertothesamplediagramabove.

Although the early outlines were drawn on paper, there are various PC project management softwares, such as Primavera, for this reason nowadays.

Step #4 – Estimate Each Activity

This could be an immediate contribution from the WBS based estimation sheet. A large portion of the organizations utilize 3-point estimation technique or COCOMO based functionpointsbased estimation strategies for tasks estimation.

You can utilize such estimation data for this progression of the process.

Step #5 – Identify the Critical Path

For this, you have to decide four parameters of every movement of the network:

  • Earliest begin time ES – The most punctual time an action can begin once the past dependent activities are over.
  • Earliest complete time EF – ES + action duration.
  • Latest complete time LF – The most recent time an action can complete without deferring the project.
  • Latest begin time LS – LF – action duration.

The drift time for an action is the time between the soonest ES and the most recent LS begin time or between the most punctual EF and most recent LF complete times.


During the flow time, an action can delay without deferring the venture complete date. The Critical Path is the longest way of the system outline. The exercises in the Critical Path have
an impact on the due date of the undertaking. On the off chance that an action of this way postpones, the venture will delay.

In case the task administration needs to quicken the undertaking, the circumstances for basic path activities reduces.

Determine the Early Start (ES) and Early Finish (EF) of activities in a PDM network diagram

Step #6 – Show Project Progress on the Critical Path Diagram

Critical way outline is a live ancient rarity. In this manner, this chart refreshes with actual values once the undertaking is completed.

This gives more reasonable figure for the due date and the task administration can know whether they are on track in regards to the deliverables.

Critical Path Method Calculations

Schedules are utilized as administration instruments to impart work arrangement, direct begin/complete dates for exercises, and to track advance on pretty much every kind of venture. In the present business universe of complex activities, chiefs can lose all sense of direction in the plenty of data gave by the undertaking plan.

While imperative terms, for example, the Early Begin Dates, Late Complete Dates, Add up to Float, or Critical Path commonly show up on PC produced plans, venture directors may not completely comprehend what they extremely mean! Accordingly, choices made by administration in view of this absence of information may not be as powerful as they could have been.

Critical Path Method Calculations (continued)

It is the conviction of the creators, that all together for development administration work force to comprehend plans and wind up fruitful in their professions, they require an intensive comprehension of fundamental booking terms. Also, to completely comprehend these essential terms, one must figure out how their qualities are computed.

This paper will talk about the essential phrasing of planning and represent how esteems are figured utilizing the Activity-on-Node (AON) estimation methods.


Since the approach of PCs, directors have produced plans for their ventures through PC booking programming bundles. Critical Path Method (CPM) plans have developed into profitable administration and specialized apparatuses for the present complex ventures. Activity-on-Node (AON) plans demonstrate the Critical Path of the calendar, and along these lines are seem to be CPM Timetables. It is through these calendars that the intelligent stream of the work grouping outlines.

What’s more, plans likewise demonstrate the arranged begin/complete dates for exercises, plan term, and flow esteems for the individual exercises on the undertaking. One should take note of that timetables could likewise organize to indicate different sorts of data, for example, planned expenses or work amounts. In any case, these choices are not in the basic scheduling discussion of this paper.

Further Calculations

It is the conviction of the creators that faculty in their particular development organizations must end up proficient in the timetable figuring process with a specific end goal to completely comprehend the significance of calendars. Thusly, venture administrators will perceive how action sequencing influences arranged begin/complete dates for exercises and the term of the timetable. Additionally, through understanding of flow values and their definitions, supervisors will have the capacity to also apply this learning in their calendar investigation should a deferral happen on the project.

CPM Calculation Plans

A plan graphically outlines the expected stream of the work arrangement and also assigns the arranged begin/complete dates for exercises once they figure. Before the dialog on the computation procedure decides to arrange begin/complete dates for exercises, plan span, and flow values for every movement started and also a clarification of essential booking wording is all together. Terms and contractions, which also appear in bracket, record below.

CPM Calculation Plans (continued)

  • Activity-on-Node (AON) diagram: An essential kind of a rationale chart utilized as a part of scheduling
  • Critical Activity: Any action in the calendar that does not have any flow; Add up to Float=0
  • Critical Path: The nonstop string(s) of basic exercises in the timetable between the Begin and Complete of the undertaking. The whole of the action terms in the Critical Path is equivalent to the Undertaking’s Span; consequently, a postponement to any Basic Action will bring about a deferral to the Venture Culmination Date.
  • Critical Path Method (CPM): Any count technique that shows the Critical Path in the schedule
  • Duration: The measure of time required to finish a timetable activity
  • Early Start (ES): Most punctual date the movement can start

CPM Calculation Plans: Part II

  • Early Finish (EF): Soonest date that the action can finish
  • Free Float (FF): The greatest number of days the action can delay without deferring any succeeding activity
  • Lag: Arranged hold up time between activities
  • Late Finish (LF): Most recent date that the action can complete immediately to the task consummation date.
  • Late Start (LS): Most recent date that the action can begin immediately to the venture fruition date.
  • Predecessor: The “previously” action; quickly precedes
  • Successor: The “after” action; instantly follows
  • Total Float (TF): The greatest number of days the action can delay without deferring the task fulfillment date.

Activity-on-Node (AON) Diagrams

Each project can separate into a rundown of individual work exercises that should be in a particular grouping. This grouping of exercises will manage the coherent request in which exercises begin or conclude. A typical method to express the grouping of the exercises is through the methods for a rationale outline.

In a rationale chart, “nodes” (squares or square shapes) speak to every action with bolts speaking to the connections between these exercises. Thus, the names of rationale outlines are “Activity-on-Node” (AON) diagrams.

AON Processes

A normal relationship in plans is the “Complete to-Begin” relationship and appears in Show 1. With this kind of relationship, the previous movement (Action An) unquestionably requires 100% completion before the succeeding (Action B) starts. As appeared in Display 1, the relationship appears by a bolt “leaving” the finish side of Action A and “entering” the start side of Action B. In this way, it is a Complete to-Begin relationship.

Activity-on-Node (AON) Calculation Method

Once all exercises are consistent and connections set, the rationale graph prepares for the computation procedure. The arrangement used to demonstrate esteems for every action appears in Show 2. TT and FF demonstrate where to put coast esteems. ES, EF, LS, LF and also the Length show where to put their individual values.

Forward Pass

The initial phase in the count procedure is the Forward Pass. In the forward pass, they ascertain the Encouraging Start and Early Complete qualities for every movement, alongside the general Undertaking Term. To encourage plan counts, a “finish of day” documentation is for both the Promising Start and the Poor Start esteems.

By doing this, the beginning of the system chart is the “finish of Day Zero”. At the end of the day, the count procedure starts with putting a zero in the Early Start (ES) position of the primary action. Whatever remains of the count proceeds with the utilization of these formulas:

  • Early Begin = Most extreme (or Most noteworthy) EF value from prompt Predecessor(s)
  • Early Complete = ES + Duration

An case of a Forward Pass computation appears in Show 3. Non specific exercises are a part of the cases in this paper to help outline the diverse figuring processes.

Backward Pass

The second step in the count includes the Regressive Pass. Through this pass, the Poor Start and Late Complete qualities compute. The equations for the regressive pass are below:

  • Late Begin = LF – Duration
  • Late Complete = Least (or Most reduced) LS value from quick Successor(s)

As the name infers, this figuring step begins at the last action in the calendar and also continues in reverse through the timetable until the point that the Poor Start esteem processes the calendar’s starting action.

To begin the regressive pass count, the EF esteem in the last movement drops down to the LF esteem. Presently the retrogressive pass recipes for poor start and late complete applies.

Float Calculations

The significance of ascertaining All out Flow and Free Flow discover the meanings of these terms. As expressed before, skim qualities show how much every individual action delays. That is, before influencing successors exercise the arranged task fulfillment date. The Flow counts for the example plan appear in Display 5. Recipes for figuring Total Flow and also Free Flow are as follows:

  • Total Flow = LS – ES (computed by LF – EF)
  • Free Flow = Most reduced ES of successors – EF

Total Flow and Free Flow

Total Flow demonstrates the distinction between the earliest and latest date the action can begin before the culmination date. Add up to flow can likewise be ascertained as the contrast between Late Complete and Early Complete, as LS short ES and LF less EF calculate precisely the same/p>

Free Flow is the measure of time that the action delays before any successors will defer. Promising Start/Complete circumstances ascertain the Free Flow values. The complete date (Early Complete) of the action contrasts and the arranged begin (Ambitious Start) of succeeding activities.

What is Total Float (Total Slack) and how to calculate it in a network diagram

Critical Path

Once the buoy esteems compute, the string of basic exercises will distinguish. This constant string of basic exercises is the Critical Path. Basic exercises are those that don’t gangs any buoy. Note the summation of the basic movement terms (Exercises A, B, D, and F in Show 5). This is equivalent to the general task span (figured in the forward pass).

This fortifies the way that a postponement in any basic movement will cause a consequent deferral in the culmination date. A timetable can have in excess of one branch or series of exercises that also make up the Critical Path.

Use forward and backward pass to determine project duration and critical path

Calculation Rules

There are normal checks to help measure regardless of whether the manual figurings are mistake free. Initially, a movement’s an incentive for Add up to Buoy can either be more noteworthy or equivalent to Free Buoy. Or then again as such, Free Buoy can never be bigger than its incentive for Add up to Buoy. Second, the Basic Way should be continuous from the main action in the calendar completely through to the last action. Third, negative numbers ought not show up for any ascertained value.

Benefits of the Critical Path Method (CPM)

Following are focal points of Critical Path methods:

  • Offers a visual portrayal of the venture activities.
  • Presents an opportunity to finish the undertakings and also the general project.
  • Tracking of basic activities.

Critical Path Method Conclusion

Critical way distinguishing proof required for any undertaking arranging stage. This gives the project management the right fruition date of the general undertaking and also the adaptability to drift activities.

A Critical Path graph should continually refresh with real data. When the project progresses, keep in mind the end goal to refine the action length/venture term predictions.

How to Calculate Critical Path: Project Management Professional (PMP)® Exam Prep

The Critical Path Method

This article also displayed the fundamental terms of planning. It also outlined how their qualities utilize the Activity-on-Node (AON) strategy for CPM booking. Timetables are administration devices to also impart work grouping. They also decide begin/complete dates for exercises and track advances on pretty much every sort of task. With the expanding interest for development venture directors, numerous organizations are employing people without a formal guideline.


Moreover, PCs and planning programming have turned out to be to a great degree reasonable and also CPM programming has fused many “ringers & shrieks” that may cause youthful colleague venture administrators harm on the off chance that they don’t comprehend the fundamental ideas of booking estimations. Clarifications introduced in this paper will be of advantage to ALL extend supervisors, youthful and also old alike. It is also related with the outline and development of the fabricated condition. This also makes them educated clients of planning software.

As you barrel forward on the path to becoming a top notch project manager, also keep this in mind. You will definitely benefit yourself if you also keep these methodologies in mind and embrace the Critical Path Method.

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