Gantt Chart Dependencies: The Complete Guide with Examples

Did you know that a significant percentage of project delays are caused by poor task dependency management? While exact figures vary, studies indicate that ineffective planning and scheduling are major contributors to project delays.

Dependencies are only half the story — over-allocated people cause just as many delays. Pair dependency management with the right capacity planning tools to keep workloads realistic across projects.

That’s where Gantt chart comes into play – it’s a useful project management tool (it dates back as far as 1910!) used to show project phases and schedules.

In this guide you’ll learn the four types of task dependencies (with real-world examples) and how to avoid common scheduling mistakes. Additionally, you’ll learn which tools handle Gantt chart dependencies best and get pro tips for managing delays and resource allocation

What Are a Gantt Chart Dependencies?

Gantt chart dependencies are the links between tasks that define the relationships between tasks – which activities must start or finish before others can begin. Let’s break down.

Gantt chart is used to visualize the tasks required for a project as building blocks. Each block represents a crucial task, and its length indicates how much time has been allocated for its completion. The longer the bar, the longer you have to complete the task. 

A dependency is a relationship between each block or task. Each individual task is dependent on several others, so some tasks must be completed before you can move on to the next.

So, in essence, a Gantt chart dependency is a way of clearly representing these relationships between tasks.

Predecessor and Successor Tasks

When creating a dependency, you need to identify the Predecessor and the Successor tasks and then work out the relationship between them.

• The Predecessor is the task that comes first. It controls the start or end date for all related Successor tasks.
• The Successor is the task whose start or end date is controlled by the predecessor.

A Gantt chart dependency is a relationship between Predecessor and Successor tasks. It’s important to note that tasks may have multiple Predecessors or multiple Successors. This is one of the main reasons for using Gantt charts to visualize these often complex relationships. Watch the following to understand more about Gantt chart dependencies.

Types of Gantt Chart Dependencies and How to Use them

There are four commonly recognized dependency types. Knowing what these are can help project managers complete tasks correctly or reschedule related tasks if any delays occur. 

1. Finish-to-Start (FS) Task Dependencies

These are probably the most common and the most easily understood type of dependency. As the name implies, you must complete task A before moving on to task B. If task A is delayed, then you must delay starting on task B. In this context, task A is usually called the Predecessor task, while task B is the Successor task. 

Example

One example of this is installing new software in a company. The company’s employees need training in how to use the software, but this cannot be done until the software has been installed. Task A (predecessor) = install software. Task B (successor) = train employees. 

2. Start-to-Start (SS) Task Dependencies

In this kind of dependency, a Successor task (task B) cannot begin until the Predecessor task (task A) has begun. This kind of dependency is not as common as Finish-to-Start, so an example will probably help here. 

Example

Say a company is in the process of rolling out a new SAP system. It is standard protocol to perform a stress test on the system before it goes live, but that cannot happen before the company has set up monitoring processes to measure the performance of the stress test. Task A (predecessor) = enable system monitoring. Task B (successor) = begin stress testing.

3. Finish-to-Finish (FF) Task Dependencies

In this case, a Successor task (task B) can only be finished after the Predecessor task (task A) has been finished. This is different from a Finish-to-Start dependency because you can start task B before task A has been completed, but you cannot finish it. This means the two tasks may run in parallel.

Example

Take the example of setting up a new IT system for a client. Task A is to connect the system to all interfaces and devices. Task B is to install and configure the software. Both these tasks can run in parallel, but you cannot finalize configuring the software until after you have finished connecting all the interfaces and devices.

4. Start-to-Finish (SF) Task Dependencies

This dependency is the opposite of the Finish-to-Start dependency. In this case, you can only finish your Successor task once the Predecessor task has been started. In other words, you can only finish task B (predecessor) after task A (successor) has started. 

Example

These kinds of dependencies are not as common as the previous three, but they do occur. Consider migrating from an outdated on-premise IT system to a new on-demand, cloud-based system. If task A is to shut down the old system and task B is to get the new system up and running, then task B can only be finished after task A has been started.  

Lead and Lag Times

Lead and lag times are also important phrases to know in the context of Gantt chart dependencies.

• Lead time is the amount of time you can start a successor task before you complete the predecessor task.
• Lag time is the time you need after completing the predecessor task before starting the successor task.

For example, if you can start a new task before the predecessor task finishes, you can apply a lead time to the new task to shorten the total project time.

Bad vs. Good Example Comparisons

Vague dependencies create costly delays. Compare these website project examples to see how proper FS specification prevents timeline confusion.

Other Project Dependencies Examples

Here are practical examples of project dependencies:

1. Finish-to-Start (FS):
   • Example: In a software development project, testing (Task B) cannot begin until coding (Task A) is complete. Coding must be finished before testing can start.
2. Start-to-Start (SS):
   • Example: In construction, installing electrical wiring (Task B) can begin as soon as the framing (Task A) starts. Both tasks can overlap, but wiring cannot start before framing begins.
3. Finish-to-Finish (FF):
   • Example: In a marketing campaign, finalizing the design of an ad (Task B) cannot be completed until the content creation (Task A) is finished. The ad design can only finish once the content is ready.
4. Start-to-Finish (SF):
   • Example: In an event planning project, the event setup (Task B) can only finish when the actual event (Task A) begins. The setup is dependent on the event’s start time to conclude.

These dependencies help in managing tasks more effectively, ensuring that work progresses in the correct sequence.

Tools with Flexible Gantt Chart Dependency Management

We’ve shortlisted the top 3 applications that have the best functionality around Gantt chart dependencies. More details on the comparison can be found in the best visual project management tools post. In this post, you will find out how we compared and selected the tools.

1. Teamhood – the most flexible and easy-to-start project planning tool with dependencies
2. Jira – most powerful dependencies for technical software development teams
3. Trello – single-level simple dependencies in Kanban board for tracking personal use or small teams

Tool Comparison Table

Key Project Management Issues Solved by Gantt Chart Dependencies

In a project, certain things must happen in a particular order for the end result to be a success. Gantt chart with dependencies can help increase a project’s chances of success by solving some key project management problems. 

1. Keeping a Bird’s Eye View of Inter-Related Tasks on Projects

Gantt chart dependencies can be used for either waterfall or Agile project planning, as they help provide an overarching view of project tasks and overall progress for senior managers and other stakeholders.

It’s true that Agile project planning values flexibility and adaptability and focuses on short-term sprint-based planning rather than extended timelines with set dates. Yet Gantt chart dependencies will still show how changing one task has the potential to impact successor tasks and, therefore, impact the product roadmap.

This is useful for Agile teams since they require stakeholder feedback, and stakeholders can get a clearer idea of project progress by tracking dependencies.

It is often assumed that waterfall project management is best suited to a Gantt chart, while Agile project managers prefer to use Kanban boards. In reality, modern project management tools allow you to use both. Learn more in this article: Kanban Gantt chart.

Whichever PM methodology you use, this bird’s eye view can be critical for gaining and keeping your key stakeholders’ buy-in throughout the project’s life.

2. Avoiding Planning Errors

By implementing task dependencies on your Gantt charts, you and your project teams can plan and delegate tasks more transparently and more easily share that information between multiple teams when needed. This makes planning more coherent and avoids any errors by structuring key activities in the right order.  

3. Scheduling Tasks Accurately

When you understand and can anticipate the task dependencies on your project, you can see how they fit together and schedule them more accurately.

• If you know task B cannot start until task A is complete (a Finish-to-Start dependency), you can schedule those tasks on your Gantt chart, with the two tasks as separate horizontal bars with no overlap.
• If, by contrast, you know task B can run in parallel with task A (a Finish-to-Finish dependency), then you can represent the tasks as separate horizontal bars that overlap. 

This enables you to calculate the time required for the project more accurately, avoid any possible scheduling conflicts, and reduce the chances of serious delays occurring. 

Consider using a Gantt Chart Maker or Task-Scheduling Software to automate such calculations.

4. Rescheduling Tasks to Take Account of Delays

When delays do occur, understanding the Gantt chart dependencies of your project can save it from failure.

When you know how each of your tasks is related, you can make adjustments to dependent tasks to account for setbacks. This means you’ll also be able to see the knock-on effect of a delay to a Predecessor task on all of its Successor tasks.

Using a Gantt chart tool with an auto-scheduling feature means it can even recalculate the dates of dependencies automatically where needed, without the need for manual intervention.

5. Reallocating Resources when Needed

Now you can reschedule tasks and adjust your project timelines to take account of delays.

This means you can also see where extra resources could be applied to speed up the completion of certain key successor tasks to help get the project back on track or avoid project overrun. This can be especially useful in a multi-team environment where you may be able to reallocate skills between teams if you can anticipate the need to do so. 

Here are some Gantt chart examples to get you inspired.

Ready to Start Using Gantt Chart with Dependencies in Your Projects?

The Gantt chart is a hugely effective project management tool when used well. Part of getting the most value out of Gantt charts is knowing when and how to track task dependencies. Now you understand the basics of Gantt chart dependencies and how to use them, you should be well-placed to start reaping the benefits. 

Learn more: Task Dependency Types and Examples.

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