Master Project Management with the Critical Path Method

Master Project Management with the Critical Path Method

Project management requires a wide spectrum of skills, organizational abilities, and attention to detail to make sure everything moves forward according to plan. A good project manager is able to keep all the plates spinning in sync while making it appear effortless at the same time.

However, the more plates you have spinning at once, the harder this is to accomplish. Critical path method (CPM) is one of the tools project managers can use to create a comprehensive plan and organize complex projects with many moving parts.

In this Process Street post, I’ll take you through the CPM process step-by-step, and then show you how our templates and checklists can take some of the stress out of your project management.

Read on, or feel free to skip ahead:

Let’s jump in!

Project management 101

To begin with, let’s do a quick overview of what project management actually involves. There are generally considered to be five stages of project management that will guide the product development process for businesses.

Stage 1: Concept

Critical Path Method: Concept
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The first part of this stage is generating ideas. These ideas can come from anywhere – employees, customers, competitors, media – but it’s important to then screen your ideas for the most viable options. You’ll also want to do some preliminary research on whether or not your idea is actually feasible. There’s no point in planning out a project you won’t have the resources to complete.

Some questions to consider when vetting your ideas would be:

  • Is this a short- or long-term project?
  • Is the project too ambitious, or not ambitious enough?
  • What are the risks associated with the project?
  • Do we have the experience to complete the project?
  • Do we have the resources to complete the project (time, labor, materials, funds, etc.)?
  • Is the project unique/have value?
  • What outcome do we expect by completing this project?

These basic questions will help guide you through choosing the best ideas for your organization and setting realistic expectations. In developing your intial concept, you may realize it’s more beneficial to start out with a smaller, simpler version and add additional features later. You may also discover that your favorite idea has already been done by a competitor, or won’t provide value for your customers.

Many projects can end up scrapped in the very beginning (read this guide on getting your proposal approved!), but for those that proceed to the planning stage, this is where the project management strategy first comes into play.

Stage 2: Plan

Once you’ve settled on an idea, you now need to come up with a strategy for completing it. Stage 2 is where you’ll set your goals and outline the scope of your project. You may already have an established process for creating your project timelines, but if not, there are two popular methods to consider.

Bill Copeland

“The trouble with not having a goal is that you can spend your life running up and down the field and never score.”Bill Copeland, poet

The first method is called S.M.A.R.T. George T. Doran developed S.M.A.R.T. in 1981 to make goal-setting more practical. Since then, it’s been widely adopted across various industries, and even featured in Peter Drucker’s Management by Objectives.

S.M.A.R.T. breaks setting goals into five core steps:

  • Specific: Who, what, where, when, which, and why
  • Measurable: Criteria to determine goal success
  • Attainable: Identify most important goals and how to achieve them
  • Realistic: Understand what it’ll take to reach your goals
  • Timely: Create a time frame for achieving the goals

For most of this post, I draw on the example of publishing a blog post, so let’s see how we could apply the S.M.A.R.T. method to creating goals for that project.

Overall S.M.A.R.T. goal: Publish a post that increases blog traffic by 20% by the end of the year.

  • Specific: Writers will use rigorous research practices and SEO optimization to create content that is accurate, actionable, and accessible.
  • Measurable: Site analytics will show a 5% increase in reading time by the end of the quarter.
  • Achievable: Each content writer will create at least one deep-dive post a month in order to provide more substantive content.
  • Relevant: Our aim is to be the best at providing our readers with interesting and informative content.
  • Timely: Each quarter, we’ll review site analytics to ensure 5% growth, and adjust accordingly if not, so we meet 20% growth by end of year.

Here we can clearly see how the S.M.A.R.T. method has enabled us to set a precise goal and detail how we plan to achieve it. If we’d said our goal was: increase blog traffic this year instead, it’s likely we wouldn’t meet that goal in the end. Goals that are vague without a strategy for completing them are inherently more difficult to complete.

Critical Path Method: CLEAR
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Some have argued, however, that the S.M.A.R.T. method hasn’t been able to keep up with the agile-centric environments of modern organizations. Adam Kreek is one such person. Kreek is an entrepreneur, motivational speaker, and Olympic gold medalist, so he knows a thing or two about setting goals.

Adam Kreek

“When we prepared for our Atlantic crossing, our higher goal was to cross the Atlantic Ocean, but we also created three rules to support that higher goal. The first rule was don’t die, the second rule was don’t kill your mates, and the third was don’t sink your boat. So look after yourself, look after each other, and look after your equipment.” – Adam Kreek

Drawing on those three rules, Kreek developed C.L.E.A.R. in an attempt to foster collaboration and unity rather than division among your team. C.L.E.A.R. stands for:

  • Collaborative: Goals should encourage team collaboration.
  • Limited: Make sure to keep scope manageable.
  • Emotional: Tap into team passions to maximize productivity.
  • Appreciable: Break tasks into the smallest possible steps that feel achievable.
  • Refinable: Stay flexible and adjust as needed.

Applying the C.L.E.A.R. method to our blog post example would look like this:

  • Collaborative: We will implement a peer review process to verify content quality.
  • Limited: We will monitor read time to identify which topics are of greatest interest.
  • Emotional: Writers will be encouraged to pitch their own deep-dive posts.
  • Appreciable: We will create a process for blog post production that follows every step of content creation.
  • Refinable: We’ll create a Slack channel to address obstacles that come up and adjust as needed.

As you can see, the C.L.E.A.R. method is more adaptable in the moment and involves much more teamwork than the S.M.A.R.T. method. Both, however, have a focus on identifying your goals, the outcome you want, and breaking tasks into the smallest possible steps. The method you choose will depend on your organization and the specific goals you’re focusing on.

The planning stage is when you’ll want to set up communication and risk management plans, but it is also when you lay out the foundation for your critical path method diagram.

Stage 3: Execute

This is the stage where you CPM will really come into play, though. CPM is a crucial tool for project managers because it will make sure the project kicks off on the right foot. CPM’s algorithms enable you to accurately predict how long the project will take, and what resources you’ll need to do so, which means you’ll be able to deliver more accurate projections while completing the project.

Stage 4: Monitor

Anything can go wrong at any time, so you’ll want to pay close attention to how the project is progressing. CPM will identify any time cushions you have in your project timeline and will assist in monitoring performance and progress.

As I’ll cover a little further down, though, CPM is not a perfect system, so close monitoring will be vital for successful completion.

Stage 5: Close

Once the project is completed, all that’s left to do is wrap up any loose ends, evaluate how well the process and budget were followed, and file your final report.

What is critical path method?
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Now that we’ve done a quick review of project management, let’s look at how CPM fits into these stages.

What is critical path method?

Critical path method is a technique used to model the essential factors involved in your project. Your project model should include:

  • Tasks required for completion;
  • Time estimates for each task;
  • Any dependencies between tasks;
  • Expected milestones or deliverables;
  • Any hard deadlines already set.

With this information, you can calculate the critical path by adding together the durations of each dependent task (i.e. any task that can’t be completed until the previous one has been finished).

Once the critical path has been calculated, you’ll be able to forecast the project’s optimal timeline for completion and better prioritize tasks and resources.

Benefits of using critical path method

Critical path method is a vital tool when it comes to project planning, scheduling, and monitoring. CPM creates a visual model of the project, which makes it easier to identify task dependencies.

By identifying these dependencies, you’re able to plan for contingencies, locate critical tasks, and manage your workflow to keep the project on track. Knowing all of these things enables you to provide more accurate data to your clients or stakeholders, and ensure you always meet your deadlines on time.

Critical path method’s flaws

You do need to keep in mind that CPM is not a perfect system. While CPM is a great planning tool, it operates on the assumption that all the necessary resources are available and doesn’t take into consideration any resource dependencies.

There is also potential for non-critical tasks to be given less attention than they require, in which case they may become critical activities that halt project progression.

As project manager, you’ll need to continuously monitor your project model for any changes and developments that may happen. Not every situation can be predicted or planned for, of course, but using the CPM will help you react promptly if the absolute unexpected does happen.

Let’s go through a practical example to see CPM at work.

Steps to effectively (and easily) use the critical path method

CPM involves a lot of math. As a result, I’m going to walk through the stages in two parts.

The first run-through will be the simple, basic, no calculator required outline of each step of the CPM. This is the version you want to look at first if, like me, math is the absolute bane of your existence (writing this post was so fun 🙄).

If, however, you are a whiz with the numbers and are prepared to get down to business, feel free to skip ahead to the algorithms in the next section.

Let’s do this!

CPM: sans math

The first step of any project is to figure out what your result should be and how you plan to achieve that.

What tasks need to be completed?
We’re finally writing that blog post. This project will only have two paths to take into consideration, but projects can have any number of critical paths that need to be followed depending on how complex the project is and how many people or departments are involved in completing it.

To define our project’s scope, we first need to list all the tasks needed to complete the project. These are the tasks needed to write and publish a blog post:

  • Outline the post
  • Request images from designer
  • Designer creates images
  • Write post
  • Images submitted for approval
  • Format the post
  • Submit for review
  • Make final edits to post
  • Make final edits to images
  • Add images to post
  • Submit for approval
  • Publish post

Now we can look at our tasks, determine which order they need to go in, and which tasks are dependent on each other.

Which tasks are dependent on each other?
The blog project is actually a collaborative effort between three people: the writer, the designer, and the editor. If we look at the tasks individually, it becomes apparent that some can only be completed after others are finished. (Later on, I’ll explain how stop tasks and approvals in our checklists can automate this process for you.)

For example, the post can’t be submitted for review before it’s written, and the images can’t be designed before they’re requested.

The next step after listing the tasks is to determine which tasks are dependent on each other. The first two tasks (Outline the post and Request images) aren’t dependent on any other tasks, and can happen in either order. However, the next two tasks are both dependent are the first two being completed.

You also need to take into consideration how long each task is expected to take. Once you know the task dependencies and task lengths, you’re ready to begin calculating the length of the critical path (the shortest amount of time a project can be completed in).

Early start/finish vs late start/finish
The early start, early finish, late start, and late finish will provide the actual time frame you’ll be working with during the project. By calculating these figures you’ll know:

  • The earliest possible point each task can be started
  • The earliest possible point each task can be completed
  • The latest point each task can begin without causing delays
  • The latest point each task can end without causing delays
  • How much “spare” time you have if a task gets delayed

Once you’ve created a diagram, you can reuse it every time you need to complete a similar project. This is particularly useful – and saves loads of time – when you frequently repeat the same processes or projects – writing blog posts, for instance.

We’ve reached the point now where we need to dive into the numbers.

Critical Path Method: Equations
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CPM: for the nerds

I’ve already mentioned some of these terms, but it’s worth reviewing them before we dig in:

  • Early start (ES): The early start will always be the first day of your project, because you can’t begin a project before it even starts.
  • Early finish (EF): This is the earliest point any uncompleted parts can be finished. This date isn’t fixed; depending on progress and any plan changes, the EF date can also change.
  • Late start (LS): The latest point that a task can start without delaying a milestone, usually the project deadline.
  • Late finish (LF): This is the latest point a task can be completed without delaying a milestone.
  • Forward pass: The calculation of ES and EF for uncompleted tasks.
  • Backward pass: The calculation of LS and LF for uncompleted tasks.
  • Network diagram: A map of the relationships between project tasks.

With that out of the way, let us begin at the beginning:

Define the project scope
First we need to list the tasks required to complete our blog post creation project.

  • Outline the post
  • Request images from designer
  • Designer creates images
  • Write post
  • Images submitted for approval
  • Format the post
  • Submit for review
  • Make final edits to post
  • Make final edits to images
  • Add images to post
  • Submit for approval
  • Publish post

Now that we know what needs to be done, we can begin calculating our critical path.

Analyze and identify the critical path
We need to examine our task list and determine which tasks are dependent on each other. For example, the graphic designer can’t create images that haven’t first been requested, and the writer can’t format a post that hasn’t been written yet. You also need to factor in how long each task will take to complete.

In creating a blog post, there are actually two paths involved: the path followed by the writer, and the path followed by the graphic designer. By looking at the task list, we can tell that the writer is responsible for more tasks than the graphic designer. However, it’s not the number of tasks but the duration that will determine which is the critical path.

Our next step is to create a network diagram of each task chronologically in relation to the other tasks. The diagram should look something like the figure below:

Critical Path Method: Network Diagram

In the diagram we can see there are two paths which take approximately the same amount of time:

  1. A + C + D + E + H + I + J = 13 days duration
  2. A + B + F + G + I + J = 12 days duration

Path 1 is our critical path because 13 days is the shortest amount of time the project can be completed in.

Having identified our critical path, we need to calculate the total float.

Float, or slack, is your wiggle room. It’s the total amount of time you can spend on a task before it affects your timeline. It’s that perfect little cushion between you and the deadline you’re hurtling toward, so you don’t go splat when you reach it.

There are actually three types of float you need to be aware of:

  • Total float: The amount of time a task can be delayed without delaying the finish date.
  • Zero float: Every task on the critical path has zero float; there’s no excess time between tasks.
  • Negative float: This is the amount of time a project is behind schedule.

The float for the critical path is zero; there’s no wiggle room. If one of the tasks takes longer than estimated, then our project will have negative float, and we may not meet our deadline.

To calculate the float for Path 2, the formula is:

Duration of the critical path – Duration of path “A + B + F + G + I + J”

Using our figures, this translates to:

13 – 12 = 1

The float for Path 2 is 1 day.

Calculate early start & early finish
Now that we know what our critical path is, and the path durations, we need to figure out the actual time frame we’re working with – specifically early start/finish and late start/finish.

The calculation for ES and EF is called the forward pass. You need to complete a forward pass for each of the project paths to get an accurate project model.

To calculate the ES and EF of each task, use this formula:

ES = EF of preceding activity + 1
EF = Task duration + ES – 1

Start with the first task of the path; in this case, it is Task A. The first task of a path is always 1.

To get the EF of Task A, the formula would be:

EF = ES + task duration – 1

Task A EF = 1 + 2 – 1 = 2

The ES of Task C (EF of previous task + 1) = 2 + 1 = 3
The EF of Task C (ES of C + duration – 1) = 3 + 2 – 1 = 4

Continue until you have the ES and EF for every task on the network diagram. Make note of the ES in the upper left corner of the task box and the EF in the upper right-hand corner. When you’ve finished, your network diagram should look like this:

Critical Path Method: Early Start and Early Finish

*Note: Task I is dependent on two preceding tasks: Task H and Task G. To calculate the ES and EF of Task I, you need to choose the preceding task with the greater EF date.

The EF of Task H is 10 and the EF of Task G is 9. So to find the ES of Task I, we’ll use the EF of Task H.

The formula for ES in this case is: EF of Task H + 1 = ES of Task I

ES of Task I = 10 + 1 = 11

The formula for EF in this case is: ES of Task I + task duration – 1 = EF of Task I

EF of Task I = 11 + 1 – 1 = 11

Calculate late start & late finish
With the ES and EF dates out of the way, we need to calculate the late start (LS) and late finish (LF) of each task. The LF of the final task on all paths (Task J) will be the same since the project ends after that task is completed.

This is called the backward pass, because it requires working backwards through the network diagram.

The formulas for LS and LF dates are:

LF of task = LS of successive task – 1
LS of task = LF of task – duration + 1

For the critical path, the LS and LF will be the same as the ES and EF dates.

To complete the backward pass of Path 2, we start with Task G.

The formula to calculate the LF of Task G is: LS of Task I – 1

= 11 – 1 = 10

LS of Task G = LF of Task G – task duration + 1

= 10 – 2 + 1 = 9

Continuing our backward pass, the formulas for Task F would be:

LF: 9 – 1 = 8
LS: 8 – 1 + 1 = 8

With all of your calculations complete, your network diagram should now look like this:

Critical Path Method: Late Start and Late Finish

That’s your project model: early start and finish dates, late start and finish dates, and total float. The first time you go through the process for your own project, it may seem complicated and confusing, but with a little practice, you’ll quickly get the hang of it.

And – even better – a good process management application can help you automate the process, so you don’t have to worry about calculation errors or delayed approvals.

Project management with Process Street

Project management is a process that your organization will undoubtedly go through many, many times, whether it’s a relatively simple process like developing an email marketing plan, or something more complex like launching a new product or service.

As with any process, it’s important to first document every step of the process, but also create a structure where that process can evolve as your organization’s needs change.

As I mentioned earlier, the critical path identifies which tasks are dependent on the completion of other tasks. When organizing a team, it can be difficult to ensure that tasks are completed in the correct order.

However, Process Street checklists have that feature built-in. Stop tasks will prevent a particular task from being completed until all previous tasks have been finished. This means you can always be sure that the project progresses in exactly the right order without anything being overlooked or forgotten.

The Approvals feature is also a useful one for project managers to utilize. This feature streamlines the approval process, making handoffs a cinch. Whoever is in charge of making the approval is sent a notification, and can then review and approve the completed work from anywhere using our mobile app.

A free Process Street account allows you to import pre-made templates into your organization, edit templates to meet your needs, or create templates completely from scratch.

Check out this webinar for a more in-depth look at what you can do with Process Street, or dive into our Getting Started with Process Street knowledge base!

Useful templates for project management

Have you used the critical path method in your project management? Do you have a different approach? Share your experience in the comments!

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Leks Drakos

Leks is a rogue academic with a PhD in contemporary fiction from the University of Kent (Paris and Canterbury). Hobbies include post-apocalyptica, street photography, and monster studies. Twitter: @leksikality [he/him]


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