What is a PERT diagram? Instructions for building PERT . diagrams

If you are a person who specializes in designing and creating ideas for projects, you are probably no stranger to the concept PERT diagramHowever, not everyone really understands the functions and uses of this type of diagram. In the article below, let CoffeeHR bring you some information you need to know to apply the PERT network diagram more effectively at work.

What is PERT network diagram?

PERT diagram (also known as PERT Network) is a type of tool used in building and managing plans/projects. This chart will show all the factors when implementing a project such as: costs, necessary tools, number of personnel... Through this graphic grid, including employees and leaders You will also understand the implementation process and identify possible problems to prepare solutions.

PERT chart will include round/square dots of different colors, to represent the main goals in a project. Each dot is defined as a step. These shapes are connected by vectors or straight lines, and the various tasks are briefly explained.

Định nghĩa sơ đồ PERT chuẩn 
Definition of a standard PERT diagram 

The current, PERT network diagram is increasingly widely used, because it is consistent with the trend of solving tasks in a model and simplified manner. PERT Network It is considered to be highly effective when used with large-scale projects.

" Read more: What is Agile?? Agile applications make project management more efficient

Situations where PERT diagrams should be used

PERT network diagram Currently, it is favored and used regularly by many companies and businesses. However, this method is more suitable when used on large-scale projects such as plans to reorganize personnel of departments, or a program to change salaries, costs... Because these plans Most of the time there will be many steps and a complicated process. Simplicity and modeling rolled into one PERT diagram will help members clearly understand what they need to do.

In addition, for projects with large investments, or coordinated with many different departments/investors, deployment based on network diagrams also helps simplify the process and support work to be done quickly. Fast, highly effective.

Nên sử dụng sơ đồ PERT với dự án lớn
PERT diagrams should be used for large projects

Understand the 4 main elements when creating a PERT diagram

One of the most important things you need to remember when creating PERT network diagram is to clearly understand the key factors affecting the work process, especially the 4 factors below:


Each event is considered a milestone marking the start or end of a certain task in the plan. In PERT diagram, these milestones are often represented by circles and numbers. The first circle is the starting event, numbered 1 and has only exit lines. And the last circle is the end event, only the representation lines enter. The circles in the middle can have both exits and entrances.


Work refers to the personnel and time taken to move from one event to another. In PERT chart, the work is the lines connecting the circles together, and the length will be estimated based on the length of the line. Unreal jobs will have a curve length of 0, and you can annotate the information on this curve.


Công việc là yếu tố cần phải quan tâm
Work is a factor that needs attention

Time reserve

Lead time is the time that allows tasks to be delayed without affecting the overall progress. This is one of the risk factors that you should mark right on the job supply curves. If the work is completed earlier than this time, it can be marked again with small dots on the arc.

Critical path

The critical path is the line that connects tasks together. The longest critical path length from the start point to the end point of PERT. The critical path is a factor that shows the progress of work. Therefore, if any element on the critical path is delayed, it means that the progress of the plan is also slower than expected.

When is it necessary to create a PERT diagram?

The manager will use it PERT chart to evaluate and complete a given project. But there are many other measurement methods, so why should we choose? PERT diagram?

For beginners, PERT charts are a suitable method when you need to evaluate the progress, required resources, and critical path of a project. We need to consider each step as follows:

  • To identify critical pathsOne of the specialties of the PERT chart that differentiates it from other methods is its ability to identify the critical path of the project. This is important when visualizing the overall timeline of a project.
  • To evaluate resources: With the unique features that PERT charts provide, you can easily see which projects require resources and which do not. This saves time on both sides of the project by providing information in advance and can be evaluated.
  • To estimate time: Because the PERT chart evaluates both individual task duration and overall project duration, it is a great tool when you need to understand expected timelines during the initial project planning stages.

Overall, create PERT chart is a good choice for a simple project plan that can be easily shared with team members. We use this chart to quickly understand progress and resources needed.

How to build a PERT diagram in project management

If you are wondering how to build PERT network How to do it properly, below is a 5-step suggested process from CoffeeHR that you can refer to:

Step 1: List all events and tasks that need to be done

If your project is too complex and has many large events that need to be resolved, you can make many different charts. Each chart is a network of work that needs to be resolved. Making a list of events will be the most important thing to help you manage the project well on the network diagram.

" Do not miss: [DOWNLOAD NOW] Work plan template by day/week/month helps increase 90%'s work efficiency

Step 2: Arrange events in order of priority

Các bước xây dựng sơ đồ mạng lưới chuẩn
Steps to build a standard network diagram

Step 3: Use lines to connect events together

from the opening event to the closing event to express the relationship. In this step, the closer the relationship between tasks is, the more detailed the diagram needs to be.

Step 4: Calculate the specific time to complete each event

The symbol for the late time is Tm and the early time is Ts. These two values are opposite but have the same scale.

First is the procedure for calculating the early timing of events:

  • The first event will have time Ts1 of 0.
  • The next event will have time Ts2, the third event will have time Ts3. The calculation formula is Ts2 = Ts2 + Ts12, Ts3 = Ts3 + Ts23 + Ts12... and so on until the last event. If there are unclear range values, the maximum index (max) will be taken.

Then there is the procedure for calculating the late times of events:

  • Start with the last event with Tm = Ts.
  • From this value, calculate back in time the events Tm1, Tm2,... similar to calculating the early time. However, if there are unclear interval values, instead of max, the min index will be used.

Step 5: Set up appropriate critical paths

Đường găng là một yếu tố vô cùng quan trọng 
The critical path is an extremely important factor 
  • After determining the specific events and time, the final step is to draw the critical path that goes through the critical events and is conventionally the longest path.
  • If the critical event is any event a, then a must satisfy the condition that the late time and early time are the same.
  • Among critical events, the event with the longest duration will be represented by the corresponding critical path.

Instructions on how to draw a simple PERT diagram

" Explore more: 5 Work report form daily, weekly, monthly most accurately

What principles should be followed when creating PERT?

When performing the setup PERT diagram, you must definitely understand the time it takes to complete the job. At the same time, representing the relationship between jobs is also extremely necessary, because it will directly affect how you allocate personnel as well as the cost of the job.

In addition, there are some following principles that you need to know when creating a network diagram:

  • One PERT network diagram Correctly, there is only one circle representing the starting event, and a second circle representing the ending event. There is only one representation line going out from the start event and only one line going into the end event.
  • The direction of each job will be represented by the direction of the arrow on the diagram. And the execution time will be correspondingly as long as the length of that curve. Therefore, the lines must be estimated in the correct length and have conventions for the base time from the beginning, not how long they are drawn.
Các nguyên tắc cần tuân thủ khi lập sơ đồ PERT
Principles to follow when creating a PERT diagram

Differences between PERT and Gantt charts

Next to PERT network diagram The Gantt chart is also a commonly used descriptive tool in project management and systems. Both of these methods work to track, set up and monitor tasks to make projects more efficient. However, there are still major differences that you should know before deciding which method you should choose:

Comparison factor PERT diagram Gantt chart
Chart format Column chart Network diagram
Inventor Henry L. Gantt Originated from the US Navy
Cases where it should be used Suitable for small projects, not too complicated Used for large-scale, high-cost and complex projects
Outstanding features Just focus mainly on the time it takes to complete given tasks Not only time but also focus on events and work to form close relationships
Nature Simple, easy to understand, easy to do It is necessary to remember many principles that are more difficult to apply. Visualizing how the critical path is presented is extremely important.

Above is some information about PERT diagram that you should know if you're working on large, large-scale projects. This diagram will be an effective method for you to complete projects more efficiently.

Scroll to Top