As a project manager, you have to juggle budgets, resources, and timelines to meet stakeholder expectations and deadlines. Successful and strategic juggling requires a clear action plan that accounts for all these things and more.
The critical path method (CPM) is a project roadmapping tool that involves identifying dependencies to create accurate timelines and efficiently deploy resources throughout the project’s life cycle.
What’s the critical path method?
Every project team experiences bottlenecks — tasks your team can only begin after completing other work. Delaying the delivery of any of these items often arrests progress and jeopardizes the project’s deadline.
In project management, the critical path is the longest string of these dependencies.
The CPM, sometimes called critical path analysis (CPA), is a technique that breaks down a complex project into individual tasks to better understand its progression. Conducting this analysis involves outlining your work breakdown structure (WBS) to:
- Identify essential tasks
- Flag constraints
- Calculate the completion time for each item
- Determine scheduling flexibility
Why is the critical path method useful?
Outlining the critical path your team must take to complete a project promotes expectation transparency so everyone feels prepared and informed. The CPM helps teams identify the following six areas:
- Focus areas: Managing a complex project is daunting, no matter how experienced you are. Systemically breaking down the project into steps lets you focus on each task, simplifying budgeting, staff allocation, and resourcing.
- Budgeting restraints: Outlining your critical path lets you identify and schedule jobs employees can complete in parallel with essential tasks, compressing the schedule and reducing the overall labor budget. And by knowing every task’s timeline, you can allocate resources to the right place at the right time, decreasing inventory storage costs.
- Strategic task allocations: Using the CPM means you can deploy the best people where they’re needed most. Experienced team members take on critical path jobs, while newer employees learn the ropes covering more forgiving, lower-priority items. And if delivery of a critical path task is in jeopardy, you can relocate someone working on an assignment with a flexible timeline to help without delaying delivery.
- Resources: By having a set timeline for the start of each activity, you’ll know exactly when you’ll need resources. You can also prioritize allocation, redirecting resources to essential tasks from lower-priority items as necessary.
- Monitoring and reporting: Using the CPM with your preferred project management software creates a project checklist and schedule you can use to assess progress in real-time. You can quickly determine if a deliverable is fully resourced and on schedule, making stakeholder reporting a breeze.
- Scope creep: Enhanced monitoring means you can spot tasks that use more than their allotted resources to avoid scope creep. When creep happens, you can enact a change management strategy to keep work within the project’s established parameters.
How to determine your critical path: 6 steps
You need a complete list of project activities to complete your critical path analysis. Refer to your project scope statement and WBS to ensure you include everything.
1. Itemize activities
Based on your WBS, document all project activities. This list provides the foundation for your critical path analysis.
If you’re creating a new video game, your list of activities might include:
| Task ID | Task |
|---|---|
| A | Market research |
| B | Game design |
| C | Backend programming |
| D | Graphics development |
| E | Graphics and programming integration |
| F | Testing |
| G | Publicity campaigning |
| H | Launch |
2. List dependencies
Once you’ve identified all project activities, determine dependencies — tasks that can’t begin until your team completes others. Also note any jobs your team can do in parallel with other activities.
| Task ID | Task | Dependency |
|---|---|---|
| A | Market research | N/A |
| B | Game design | A |
| C | Backend programming | B |
| D | Graphics development | B |
| E | Graphics and programming integration | C, D |
| F | Testing | E |
| G | Publicity campaigning | E |
| H | Launch | F |
3. Draft the network diagram
Next, create the network diagram — a flowchart that maps out each activity chronologically. Place each task in a box and connect the boxes with arrows based on dependencies. Keep adding boxes and arrows until you’ve plotted the entire project.
4. Estimate the timeline
To determine the longest sequence of critical tasks, you must estimate completion times for each activity. You might base estimates on the following:
- Past experience and knowledge
- Previous project data
- Industry standards
Alternatively, you can base estimates on the forward or backward pass technique.
Forward pass
Using a previously defined start time, calculate early start (ES) and early finish (EF) times for each task. The first task in the critical path has an ES of 0. The highest EF of a task’s predecessor defines its ES, so EF = ES + task duration and continues through the sequence.
This technique helps you determine resource allocation dates.
Backward pass
Beginning with the last WBS activity, you'll use the backward pass method to determine the late start (LS) and late finish (LF) of the previous list item, moving through each preceding task, so LS = LF – task duration.
A backward pass identifies timeline risks by pinpointing the last possible moment work can begin on a task without delaying delivery.
| Task ID | Task | Dependency | Duration |
|---|---|---|---|
| A | Market research | N/A | 10 days |
| B | Game design | A | 30 days |
| C | Backend programming | B | 20 day |
| D | Graphics development | B | 20 days |
| E | Graphics and programming integration | C, D | 15 days |
| F | Testing | E | 10 days |
| G | Publicity campaigning | E | 30 days |
| H | Launch | F | 1 day |
5. Calculate critical path
Usually, your project management software will have a built-in function to calculate your critical path. If you prefer to do it manually, the calculations are pretty straightforward:
- Write down the start and end times of each task. Task A’s start time is 0, and its end time is its duration.
- The next activity’s start time is the end time for the predecessor in the critical path. Its end time is the start time plus duration.
- Continue calculating until you’ve accounted for all tasks.
The end time for the entire project is the total duration of the longest sequence of activities — the critical path.
6. Determine float
The amount of time you can delay an activity without impacting the project’s completion date is known as “float” or “slack.” Use project float to manage risks and deal with unexpected issues throughout the project life cycle.
Critical path items have zero float because their schedule is set and unadjustable. But you can delay and sometimes skip parallel items, tasks that can happen concurrently with the critical path, without impacting your deadline when short on time or resources.
There are two types of float:
- Total float is how long you can delay an activity from its ES without affecting the project schedule.
- Free float occurs when two or more tasks share a common successor and refers to the time you can delay one task without impacting the other’s delivery.
How to apply the critical path method: 3 steps
Thanks to the CPM's built-in visibility around your project timeline, you’ll have the information to proactively manage your schedule and adjust at the earliest sign of trouble. Here’s how to use the CPM.
1. Compress the project timeline
Due to unforeseen circumstances, you might have to move up a project’s deadline. It’s not ideal, but you can accomplish this in two ways:
- Fast-tracking: The CPM identifies a list of parallel activities. Team members can work on these items simultaneously with other critical path tasks, speeding up completion time.
- Crashing: If your scope allows, reallocate resources to critical path activities to speed up production. Be sure to notify stakeholders of the change, especially if you need to obtain additional resources.
2. Respond to resource shortages
Sometimes, unexpected roadblocks or changes reduce available resources. When that happens, you need to reallocate what’s left through resource leveling techniques. Resource leveling involves shifting a task’s start and end dates to accommodate availability changes. You can either apply resource leveling only to tasks with a float, or adjust the timeline on the entire critical path.
3. Compile data
By tracking the actual activity duration against your estimates, you can identify bottlenecks in project development and gain more accurate timelines for individual task completion. Accumulating this knowledge into a data pool of precise time requirements and sharing it with other project managers helps everyone create fact-based schedules for future projects instead of relying on best guesses.
A critical path example
Going back to the game-design project, the critical path would look like this:
|
START Market researchDuration: 10 days ES: 0 days EF: 10 days Game design Duration: 30 days ES: 10 days EF: 40 days |
||
|
Graphics development Duration: 20 days ES: 40 days EF:60 days |
Backend programming Duration: 20 days ES: 40 days EF: 60 days |
|
|
Graphics and programming integration Duration: 15 days ES: 60 days EF: 75 days |
||
|
Testing Duration: 10 days ES: 75 days EF: 85 days |
Publicity campaign Duration: 30 days LS: 55 days LF: 85 days |
|
|
Launch Duration: 1 day ES: 85 days EF: 86 days |
||
| Critical path activities | ||
| Parallel activities |
The total duration of the critical path is 86 days.
Using the critical path method to roadmap a project
By following the CPM, you’ve done most of the work necessary to create a project roadmap. You’ve listed the essential tasks, constraints, order, and duration. All that’s left is to upload that information into a project management software like Roadmunk by Tempo to bring your project to life. Roadmunk creates a stakeholder-ready visual representation of your project plan in minutes.
And it doesn’t stop there. Jira-enabled Timesheets by Tempo let you monitor team activities, review employee availability, and redeploy tasks if needed.
