What is a drillable Gantt chart?

The one chart that serves the boardroom and the delivery stand-up — without maintaining two versions that drift apart.

A drillable Gantt chart is a Gantt chart where each phase can collapse into a single summary bar or expand to reveal the tasks underneath it — toggled live, in one click. Collapsed, it's a clean five-phase overview for executives. Expanded, it's the full task-level plan for the delivery team. Same chart, same source of truth, two audiences.

It exists to kill a specific, familiar pain: the two-deck problem.

The problem it solves

Executives want the shape of the program — five or six phases, key milestones, what's at risk. The delivery team wants every task, owner and dependency. So most project managers maintain two artifacts: a tidy exec slide and a detailed plan. They immediately start to drift, and by the third status cycle they disagree with each other. A drillable Gantt collapses both into one chart, so there's nothing to keep in sync.

How it works

Group your tasks into phases. Each phase gets a ▶ / ▼ toggle:

• Collapsed (▶): the phase shows a single summary bar. Its start is the earliest child task's start, its end is the latest child's end, and its progress is the duration-weighted average of all children — so the summary is always correct without any manual maintenance.
• Expanded (▼): every child task appears with its own bar, dates and owner.
• Dependencies stay smart: arrows pointing into a collapsed phase re-route to the summary bar's edge, then snap back to the real task when you expand — the logic never breaks.

Why static tools can't do this

A Gantt built in PowerPoint or Excel is a picture: there's no live collapse, so you're back to maintaining two versions. Drilling requires the chart to compute the summary from its children on the fly — which is exactly what GANTT360° was built to do, and the feature no other browser Gantt tool offers.

One chart serves both the steering committee and the delivery team. No second version to keep in sync.

— The GANTT360° philosophy

If you present the same plan to two audiences, this is the feature that saves you the most time between meetings. See it in the steering-committee workflow, or try it free on your own plan.