Estimate a project timeline
Estimate a project's timeline with uncertain dependencies. Separate work from waiting, explain the range and allow extra time for specific risks.
Count work and waiting separately #
A task can take two hours of work and still need three calendar days. Estimate the time spent doing the work, then account for approvals, queues, integration windows and supplier replies that affect the finish date.
Keep both numbers. If the project runs late, you can check whether the work took longer, a dependency kept you waiting or a risk became a real problem.
Sources: Estimate active effort and elapsed time separately · Put the slow external dependency on the forecast
Show the waits you depend on #
If another team, customer, supplier or approver must act before you can finish, include that wait in the forecast. Keep it separate from the task owner's work estimate; use it to explain the timing, without assigning blame.
If the wait is uncertain, show that uncertainty. Do not present a fixed response time you cannot support.
Narrow the range when evidence changes #
Make the range narrower when you have resolved a meaningful unknown: tested an interface, chosen a design, received approval or checked an important assumption. The passing of time alone does not justify a tighter estimate.
A wide range also needs a next step. Name the observation or test that could help you narrow it.
Sources: Let ranges narrow only when uncertainty is actually removed
Tie extra time to specific risks #
If you add a buffer, explain what it covers. Name the remaining risks: rework, integration problems, delayed approval, poor data or an unknown amount of data to migrate.
Some risks do not support a reliable probability. A plain rule for allowing extra time can be more honest than a precise figure with no evidence.
Update the forecast for a reason #
Change the forecast when an input, assumption or risk changes, and say which one changed. Pressure to deliver sooner is not evidence that the work will finish sooner.
If management chooses a different delivery promise for business reasons, label it as a new commitment. Keep the forecast tied to the available evidence.
Sources: Re-estimate when evidence changes, not when anxiety spikes