Understanding PERT vs. CPM (With Definitions and Benefits)

Updated August 28, 2023

Project management involves planning, scheduling, and monitoring several aspects of a project to meet defined objectives. PERT and CPM are two project management techniques that exhibit the flow and sequence of project activities. Understanding the characteristics and differences of PERT and CPM can help you adopt the most effective technique for an organization's projects. In this article, we discuss why to learn about PERT vs. CPM project management techniques, explain what a PERT chart is, describe its benefits, explain what a CPM is, discuss its benefits, and explore the key differences between PERT and CPM.

Why learn about PERT vs. CPM project management techniques?

You can learn about PERT vs. CPM scheduling methods to decide which one to implement depending on a project's specifications and end goals. For instance, PERT is ideal for projects without designated due dates or timeframes to complete certain activities. In contrast, CPM is appropriate for projects with a specified duration. While both techniques help design networks and determine a project's critical path, they differ in specific areas and offer different benefits to a project.

What is a PERT chart?

PERT is an acronym for program evaluation and review technique. A PERT chart is a visual management tool for tracking and monitoring project tasks and timelines. PERT uses time as a variable that represents performance specifications and resource application. In this technique, you first divide the project into activities to form a sequence. Then, you calculate the time needed to complete each action. This method examines and represents all activities of a project. This is usually to identify the least possible time to complete each task and the minimum time it can take to complete the entire project.

Project managers often use this chart to make realistic schedules by setting estimates for each duration. PERT uses the following three-time estimates to get the expected activity time for planning projects with uncertain activity durations:

Optimistic time: This is the shortest estimated time to complete a project activity. The optimistic time estimate shows the minimum time based on an analysis of the best-case scenario.
Most likely time: This is the completion time with the highest probability. Professionals make this estimate based on the given time duration, assigned resources, productivity levels, project dependencies, and possible interruptions.
Pessimistic time: This is the longest it can take to complete a project activity. It's the maximum project duration based on worst-case scenario analysis.

Benefits of PERT in project management

PERT helps identify early starts, late starts, and possible slacks for each project task. Because it focuses on setting time estimates, it provides the probability of completing projects before the predicted date. Here are more benefits of using a PERT chart in project management:

Manages project uncertainty

The major benefit of using the PERT is managing uncertainties in a project. It estimates the time required for each task to get a nearly accurate measure of the project completion time. Using a PERT chart can help project managers see the entire project timeline and recognize various aspects that can improve to minimize the estimated time. PERT uses the three tome estimates to calculate the expected activity time using the following formula:

Expected activity time = (Optimistic time + (4 × Most likely time) + Pessimistic time) / 6

Assumes all initiated projects as new

The PERT chart assumes every project to be new, with no previous templates or data. Managing a project without particular referencing can allow for more creative ideas to increase project efficiency. The ideas and methods implemented can help in optimizing total project procedures.

Improves planning and decision making

Using a PERT chart can promote the effective presentation of data across various departments. The qualitative and qualitative data collected from all sources can improve your planning and decision-making processes. It can also facilitate effective communication between departments and better coordination of project activities.

What is CPM in project management?

The critical path method (CPM) in project management is a technique used to oversee projects where there's a specific time required to complete a project. Project managers use it to determine the critical and non-critical tasks that can help reduce conflicts and achieve desired results. CPM identifies essential activities to ensure no delayed actions can affect the entire project.

When using CPM, managers start by preparing a list of all activities needed to complete a project. Next, you can estimate the time required to complete each activity and determine the dependencies between the activities. You can then define the path as a sequence of activities in a network. CPM typically involves choosing the path that requires the least amount of time and is cost-effective in a project. Many industries use CPM, including software, construction, aerospace, and technology industry.

Benefits of CPM

Project managers often use CPM because it gives valuable insight into resource allocation for each project task. It also provides an outline for the long-term coordination and planning of the project according to a specified timeframe. Project planning, scheduling, and controlling are often more effective with a CPM, improving the project's productivity. You can use this technique to compare project expectations with actual progress and confirm project efficiency. Here are more benefits of using CPM in project management:

Facilitates enhanced task scheduling

This technique facilitates task prioritization, giving teams a better strategy for deploying resources effectively. CPM shows where to spend more time, effort, and resources to accomplish project goals quickly. It can help you recognize the actions to complete first to enable you to complete the project faster and indicate the tasks you can delay without affecting the overall project plan. This helps you schedule tasks according to the project's immediate needs, facilitating enhanced task scheduling.

Measures project progress efficiently

CPM network divides large projects into a series of discrete tasks, which can help measure project progress efficiently. You can assess every project activity to ensure you're allocating resources effectively. It also shows how to find additional resources to improve project time or an effective alternative to reduce costs and remain under budget.

Helps in cost and budget control

CPM associates costs and resource allocation with each sub-task. This helps monitor the expenses on every task and ensure they're all within the allocated budget. The technique identifies when a project exceeds the planned budget or experiences delays in the planned schedule and notifies you instantly. This can help you recognize strategies and areas that need changes or adjustments and address them accordingly.

When you allocate budgets to each sub-task rather than for the entire project, it's easier to recognize financial issues or constraints and resolve them effectively. This helps ensure you complete the project within the pre-defined budgetary parameters.

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PERT vs. CPM

Here are the significant differences between PERT and CPM:

Technique: PERT is a project management technique used to measure uncertain activities in a project and focuses on time planning and control. In contrast, CPM is a statistical project management technique that manages the well-defined activities of a project, such as time and cost management.
Focus: PERT focuses on minimizing the time required to complete a project by the designated deadline. In comparison, CPM focuses on a trade-off between cost and time with a significant emphasis on minimizing costs.
Evolution: PERT evolved as a suitable technique for research and development projects, while CPM is best suited for non-research projects like construction.
Orientation: While PERT is event-oriented because it focuses on time, CPM is often activity-oriented.
Model: PERT uses a probabilistic model, while CPM is a deterministic model.
Time estimates: PERT has three-time estimates and helps make high-precision time estimates. In contrast, CPM has only a onetime estimate and is appropriate for reasonable time estimation.
Activities type: While the PERT technique manages unpredictable activities, the CPM can manage predictable activities effectively.
Job nature: PERT is beneficial for the non-repetitive types of jobs, while CPM involves jobs with a repetitive nature.
Crashing concept: Crashing is a compression technique used in CPM to reduce the project duration and associated costs. In comparison, the crashing concept does not apply to PERT as there's no time certainty.