Gantt chart

What it means

A Gantt chart lays a project out as bars on a time axis: every task shows its start, its end and how long it runs. Arrows between the bars say what waits for what, and the critical path falls out of them.

It is not a plan of scope and not a plan of people. What has to be done belongs in the brief, who has time for it in capacity planning and the direction for the years ahead in the roadmap; the chart answers only when.

It differs from kanban in what it measures: kanban shows the state of the work and where it piles up, a Gantt chart shows dates and dependencies. For work that arrives continuously and never ends, such as routine bookkeeping of documents, it is pointless. It suits a one-off project with a clear start and finish.

How it works in practice

It is drawn wherever a date promises something to somebody: an accounting system going live, books taken over from the first of the month, construction under a works contract, or the timetable inside a grant project. The bars are pinned to milestones the customer signs off.

It earns its keep only when the original version sits next to the current one. The comparison shows how many days the project has slipped and which task caused the slip, which is material for a supplier meeting rather than a picture on the wall.

We plan even the year-end close of a larger client as a small project: stocktake, reconciliation of the sub-ledger, accrued estimates, audit, approval and filing of the tax return. The auditor’s bar cannot start until the trial balance is ready, and at the end sits a statutory deadline that does not move, so every delay at the front eats time at the back.

What to watch out for

A chart drawn once at signature and never updated costs money wherever the timetable binds: under a grant, work done after the end date turns into an ineligible cost that has to be repaid, and a works contract runs a contractual penalty for every day of delay.

The chart will happily draw three parallel tasks for the same person or team. Until the plan is checked against real capacity it looks realistic, but it slips within the first weeks, and the date agreed in the works contract is then held only through overtime, or not at all.