How Critical Path Method Drives Project Management Success
Some projects may consist of hundreds of tasks and dependencies. Sometimes it is not easy to identify the most important tasks and meet their deadlines. Do you know the method that can solve this problem?
What is the critical path method?
Critical path method (CPM) is a step-by-step management technique for project processes planning. It identifies critical and noncritical tasks and prevents timeframe problems.
If you are an experienced project manager, you have heard the term “CPM” for sure. If the subject looks new, it’d be better to start with some definitions.
- Critical path in project management is the series of tasks that must be done in order and in the right amount of time.
- Float (slack) is the amount of time that a schedule activity can be delayed or extended from its early start date without delaying the project ﬁnish date.
- Schedule diagram is a graphical representation of the project’s logical relationships.
What is a critical path in project management analysis?
With the help of Gantt Charts, the critical path method helps project managers to plan and schedule all tasks and activities that must be completed in a project in different spheres including research, IT, construction, etc.
Today you can find many helpful texts about CPM in project management books that can help you to get project success. Here we would like to share how to calculate critical path, how to identify critical paths in diagrams, list some of the benefits and limitations of CPM and show some examples.
Critical path management origins
The critical path method as a part of project management was developed 60 years ago in the United States. It was used for critical path scheduling of agricultural and factory projects and construction work. Nowadays CPM is adapted to different fields including software and hardware development.
Critical and noncritical tasks and objectives
If you can delay a part of your task without postponing work on other activities, it is not a critical task. Your tasks are critical if they cannot be delayed and you identify them in the project by time constraints.
Critical path project management. How to calculate critical path?
Let’s have a look at a simple example. Critical path project management works perfectly for the projects with short deadlines. So let’s say the purpose of our project is to plant a garden in a backyard. Now we need to set all the ways and steps that will show us how to grow the first tree.
To complete this project successfully we need to list all the tasks that should be done:
- Choose a place in the backyard
- Buy a shovel
- Choose the right seeds
- Dig a hole
- Fill the hole with water
- Plant a tree
As you can see, some of the steps cannot start before the others are finished, because they are dependent on others. The steps “Dig a hole”, “Fill the hole with water”, “Plant a tree” are sequential activities, because they must be done in a specific order.
In our example, these 3 steps and the first one (“Choose a place in the backyard”) are the most important critical steps to get the solution. And they should be placed on the critical path for our project.
The main idea here is that we cannot start some activities or steps until the others are finished.
Now it’s not difficult to calculate the length of the project. We can determine the approximate start time for every step on the critical path.
- Choose a place in the backyard – 30 minutes
- Buy a shovel – 30 minutes
- Choose the seeds – 30 minutes
- Dig a hole – 10 minutes
- Fill the hole with water – 5 minutes
- Plant the tree – 15 minutes
If we summarize the durations of all the critical tasks, we will get the time that we need to complete our project. In our critical path example, we need 2 hours.
Critical path analysis
A critical path analysis helps to predict if a project will finish on time.
The main benefits of critical path analysis
How does the critical path method help project managers to get success?
- It demonstrates the graphical view of any project.
- It helps to identify the most important tasks that you have to manage.
- It helps to save your time and reduce timelines.
- It helps to compare planned and actual progress.
- It helps to make dependencies visible and clear.
- It helps to plan, schedule and control your projects.
- It helps to identify all critical activities that need your special attention.
Looks helpful, right?
But despite the fact that the critical path method is the useful PM technique, it has some limitations. It does not consider dependencies between resources. You pay less attention to non-critical activities. But sometimes they can become critical. The projects with a critical path can often be uncompleted within the required time duration, and so on.
How to calculate a critical path in project management?
A critical path analysis is a powerful tool that can help you to schedule and manage any project. The process consists of six steps. Have a look at how CPM project management can be used in practice.
6 Key steps in CPM planning
The 1st Step: Make your activities specific
Start to identify every task in your project. The list of specific activities should include only higher-level activities. It will divide the tasks into manageable sections. Your structure may look like lists, tables or tree structures.
The 2nd Step: Set dependencies
Some activities will start when others are complete. If you list the predecessors of every activity, it will help you to identify the correct order.
The 3rd Step: Visualize a critical path
How to make a network diagram?
Now you have your identified activities and the dependencies, so you can draw the critical path network diagram (the critical path analysis chart).
Project managers use critical path network diagrams to get a view of projects broken down into separate tasks. Boxes, arrows and circles help to visualize the activities and dependencies. You should name each activity and highlight the paths.
There is no need to draw CPM diagrams on paper because you can use the helpful software for this purpose.
The 4th Step: Estimate the time of activity completion
Even if you have not enough experience, you may try to estimate the time that required completing all your activities. The measure can be a day or a week. It depends on how small or complex your projects are.
The 5th Step: Find critical paths
To identify a critical path you need to determine the main parameters of your activities.
- The earliest start time (ES) is the time when an activity can start once the previous dependent activities are completed.
- The earliest finish time (EF) is ES + the period that required to complete the activity.
- The latest finish time (LF) is the time when an activity may be completed without any delays.
- The latest start time is LF – the period that required to complete the activity.
Pay attention to the float time – the time between ES and LS or between EF and LF. During this period, your activity can be delayed without delaying the finish date of the project.
Using the network diagram, you can identify the longest path of any activity and the longest sequences. If you need to accelerate your project, you should reduce the time for critical path activities.
In case you have several critical paths, you will have the higher probability of the schedule changing.
The 6th Step: Update your diagram and watch the progress
The diagram should be updated to give you a chance to recalculate a critical path. Now you will have a more realistic view of your project.
Why do project managers use CPM?
PMs get the necessary information about the project’s optimistic duration.
- They can manage the tasks that need strong control.
- They can add limited resources to the project objectives and recalculate the value of a critical path.
- In case of terms’ failure, they can quickly predict how to change them and meet the deadlines.
The process of identifying the critical path in projects continues to get easier. When CPM was created, managers had to identify a critical path by hand. Now you can save your time and avoid drawing tables and nodes, using the critical path software programs and apps.
Critical path calculator
You can choose at least two ways to delegate it to software – rely on your Gantt chart software and enable this option in settings (like in GanttPRO) or use some other calculators.
If you rely on external tools to calculate the critical path, you need to fill in the following information: successors, predecessors, duration, early start time, early finish time, latest start time, latest finish time and slack time.
After that your critical path will be calculated.
Gantt Chart critical path calculation with Excel
If you are planning a small project and need to identify critical paths, Excel can be a solution. The following steps will help to calculate critical paths and make the CPM schedule:
- Build a diagram
- Prepare the spreadsheet in Excel
- Identify the critical path
- Create a critical path Gantt Chart
Find out more about the Excel critical path method scheduling:
CPM with GanttPRO
How to identify the critical path for our project with GanttPRO?
As you can see, planning projects with Excel does not save your time. Creating a Gantt Chart requires some time here. GanttPRO can do this work for you. It will be easy to identify the critical path with just a couple of clicks.
At first, create your project and set all the tasks with the help of GanttPRO tools. Open any task, set start and end dates, durations and identify all predecessors.
Then you click “Settings”. Display the critical path in the GanttPRO chart view. You’ll see the shortest time in which the project can be completed and the most important tasks.
If you try to apply the CPM scheduling to your project management, you will see that the critical path identification is required for any planning phase. It gives us the correct completion date of projects and the flexibility to float activities.
To sum up and remind you once again that the critical path analysis is a powerful and effective method of assessing:
- Your tasks that must be carried out. Task priorities.
- All parallel activities.
- The sequence of scheduling and timing.
- The shortest time for your project to complete it.
- All resources that you need to achieve the goal, etc.
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