Dependencies and types of dependencies
Learn how task dependencies work in Gantt Suite and understand the four standard dependency types used to build accurate project schedules.
What is a dependency?
A dependency is a logical relationship between two project tasks or milestones that defines the order in which work should be performed.
Dependencies help build realistic project schedules by ensuring that related tasks are completed in the correct sequence.
For example, a testing task may depend on the completion of a development task, meaning testing cannot begin until development is finished.
Standard dependency types
Gantt Suite supports the four standard dependency types used in project management.
Finish-to-Start (FS)
A Finish-to-Start dependency means that the predecessor task must finish before the successor task can begin.
In other words:
Task B cannot start until Task A has finished.
This is the most common dependency type and is considered the standard relationship for project scheduling.
Finish-to-Finish (FF)
A Finish-to-Finish dependency means that the predecessor task must finish before the successor task can finish.
In other words:
Task B cannot finish until Task A has finished.
Start-to-Start (SS)
A Start-to-Start dependency means that the predecessor task must start before the successor task can start.
In other words:
Task B cannot start until Task A has started.
Start-to-Finish (SF)
A Start-to-Finish dependency means that the predecessor task must start before the successor task can finish.
In other words:
Task B cannot finish until Task A has started.
This dependency type is rarely used in practice.
Dependency comparison
Dependency | Meaning | Typical use case |
|---|---|---|
Finish-to-Start (FS) | Successor starts after predecessor finishes. | Development → Testing |
Finish-to-Finish (FF) | Successor finishes after predecessor finishes. | Documentation completed together with project completion |
Start-to-Start (SS) | Successor starts after predecessor starts. | Parallel development activities |
Start-to-Finish (SF) | Successor finishes after predecessor starts. | Shift handovers or operational transitions |
Best practices
For most projects, Finish-to-Start (FS) should be the default dependency type.
Project scheduling standards recommend using Finish-to-Start relationships whenever possible because they produce the clearest and most predictable schedules.
Use Start-to-Start, Finish-to-Finish, and Start-to-Finish dependencies only when they accurately represent the work being planned.
Ideally:
Every task should have a logical predecessor, unless it is the first task in the project.
Every task should have a logical successor, unless it is the final task in the project.
Use non-FS dependency types sparingly and only when their scheduling behavior is well understood.
Tip: Well-defined dependencies improve schedule accuracy, make the critical path more meaningful, and enable Gantt Suite's automatic scheduling features to produce more reliable project plans.