Gantt Project End Date Calculator
Add up a list of back-to-back task durations from a start date to find a project’s finish date — counting working days and skipping weekends.
How it works
total duration = sum of all task durations (tasks run one after another) · end date = the (total)-th qualifying day counting the start day as day 1 · working-day mode skips Saturdays and Sundays; calendar mode counts every day
For a simple sequential (waterfall) plan where each task starts when the previous one ends, the project length is just the sum of the task durations, and the finish date is that many days out from the start. In working-day mode weekends are skipped, matching how project-management tools schedule effort, and a start date on a weekend is nudged to the following Monday. This assumes no parallel tasks, gaps or dependencies beyond a straight chain — for overlapping tasks the true finish is driven by the longest dependency path (the critical path).
Worked example
Starting Tuesday, September 1, 2026 with tasks of 5, 3, 8, 2 and 6 working days — 24 working days in total — the project runs day 1 on September 1 and finishes on its 24th working day, Friday, October 2, 2026, spanning 32 calendar days once the weekends are included.
Frequently asked questions
Does it account for overlapping tasks?
No — it assumes tasks run strictly one after another. If tasks overlap or run in parallel, the finish date is set by the longest chain of dependent tasks (the critical path), which is typically shorter than the simple sum this uses.
What about public holidays?
Working-day mode skips only Saturdays and Sundays. It does not remove public holidays, so subtract any holidays in your schedule, or add their days to a task, to get a fully accurate finish date.
Why does the start date sometimes move?
In working-day mode a project cannot begin on a weekend, so a Saturday or Sunday start is shifted to the next Monday before counting begins. Calendar mode keeps your exact start date.
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This calculator is for educational purposes. Double-check important results before acting on them.