A WBS organizes your project's scope; a Gantt chart schedules it. Learn how to convert a work breakdown structure into a working Gantt chart timeline step by step.
A Work Breakdown Structure (WBS) and a Gantt chart solve adjacent problems. The WBS answers "what needs to be done"—it decomposes the project scope into a hierarchical list of deliverables and work packages. The Gantt chart answers "when does it happen"—it schedules those work packages on a timeline with durations, dependencies, and resource assignments.
Skipping the WBS and jumping straight to a Gantt chart often means the schedule misses entire categories of work. Building a WBS without converting it to a Gantt chart means you have a scope document with no execution plan.
The correct sequence: WBS first, then Gantt chart.
A WBS breaks the project into levels:
Level 1: The project itself (e.g., "Website Redesign")
Level 2: Major deliverables or phases (e.g., "Discovery," "Design," "Development," "Launch")
Level 3: Work packages within each phase (e.g., under "Design": "Wireframes," "Visual design," "Prototype," "Design review")
Level 4 (optional): Tasks within work packages (e.g., under "Wireframes": "Homepage wireframe," "Product page wireframe," "Checkout flow wireframe")
Each item at the lowest level—called a work package—is what you'll convert into a Gantt chart task. If your WBS goes four levels deep, the Level 4 items become Gantt tasks. If it only goes three levels, Level 3 items become the tasks.
Start by listing every work package from your WBS as a flat list. This becomes your Gantt chart task list. Don't worry about order or dates yet—just get every item on the list.
For the website redesign example:
In your Gantt chart, organize the flat task list back into the WBS phases. Use summary rows (parent tasks) that match your WBS Level 2 categories. This maintains the hierarchical structure of the WBS while adding time dimensions.
In gantt-chart.io, create a row for each phase ("Discovery," "Design," "Development," "Launch"), then add the work package tasks as children within each phase.
Now add time estimates. Work packages without time estimates are the most common gap between a WBS and a usable schedule.
For each task, estimate:
Use the most likely estimate in your Gantt chart. Note the worst case duration for tasks on your critical path—those are the ones that can blow your end date if they slip.
If you're uncertain about an estimate, pad it by 25-30%. It's better to deliver early than to replan constantly.
Go through your task list and identify which tasks can't start until another is complete. This is the dependency mapping step—it's what transforms a list of tasks into a network of interconnected work.
Common dependency types:
In your website redesign example:
Add dependency arrows in your Gantt chart on gantt-chart.io to connect these tasks.
With tasks, durations, and dependencies in place, set your project start date and let the dependencies drive the rest. The Gantt chart will automatically sequence tasks based on dependencies.
Review the resulting timeline:
Before finalizing, check your Gantt chart against the original WBS:
This validation step is where you catch the errors that cause project overruns—work that was in the WBS but accidentally omitted from the schedule.
As work progresses, the WBS and Gantt chart should stay aligned. When scope is added:
When scope is removed:
This two-document discipline—WBS for scope, Gantt for schedule—prevents the common failure mode where the schedule grows without formal scope acknowledgment.
If you have a WBS document already, the conversion to a Gantt chart takes 1-2 hours for a medium-complexity project. Open gantt-chart.io, create your phase rows, add your work package tasks, estimate durations, add dependencies, and set your start date.
The result is a project plan where every task traces back to an approved scope item—and every scope item is scheduled on a timeline.