Project Timeline Calculator

Direct answer

Add the sequential work, review and explicit contingency days. The GAO schedule guide explains that credible schedules need rational activity durations and dependencies; this tool provides only a visible arithmetic total for the days you decide to include.

Variables and formula

• Sequential work days: work that cannot start until the preceding step finishes.
• Review days: feedback, approval and rework time included in the plan.
• Contingency days: reserve explicitly added to the schedule.

Planned timeline = Sequential work days + Review days + Contingency days

Reproducible example

A plan with 20 work days, 5 review days and 3 contingency days totals 20 + 5 + 3 = 28 days, or four seven-day weeks.

Interpretation

The contingency share makes the reserve visible rather than hiding it inside task estimates. A duration total does not prove that the plan has a valid critical path or enough people to deliver it.

Assumptions and limitations

• Entered work is sequential.
• A day uses the calendar convention chosen by the project team.
• Dependencies, parallel work, holidays, capacity and scope changes are excluded.

Common mistakes

• Adding parallel tasks as though they must happen one after another.
• Omitting review and rework time.
• Treating a reserve percentage as a prediction of delay.

Assumptions

• Entered work is sequential rather than parallel.
• A day means the planning day selected by the project team.
• Dependencies, staff capacity, holidays, calendars, scope changes and critical-path analysis are outside this simple duration total.

Sources and methodology

CalcMotive publishes the formula and assumptions so you can decide whether the estimate fits your use case. See our methodology standards.

• Schedule Assessment Guide: Best Practices for Project Schedules; U.S. Government Accountability Office; accessed Aug 13, 2026