Project Finish Date and Critical Path
Calculate a project's earliest finish from task durations, predecessors and a work calendar. See critical tasks, one critical path and task slack.
Starts with an editable example. Replace the dates and rules with your own.
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Select your counting rules and calculate.
Calculation details
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How to use this calculator
Enter a project start and working calendar. Give each task a unique short ID, a duration in whole working days and optional predecessor IDs. Add a target finish if useful.
Tasks begin after all predecessors finish. Independent tasks run in parallel with unlimited resources. Slack is measured against the earliest overall finish. Unknown IDs and dependency cycles are rejected; shared staff and equipment are not automatically leveled.
A worked example
A takes two days; B takes three after A; C takes one after A; D takes one after both. The critical path A–B–D takes six working dates, finishing November 9 from November 2, 2026.
Can a project have more than one critical path?
Yes. The result shows one path and identifies every zero-slack task, so parallel critical branches remain visible in the task breakdown.
Which calendar and years are supported?
Use Gregorian dates from 1900 through 2100, with results in that range. Daily attendance, office, coverage and chore plans allow up to 366 dates; school cycles, course plans and milestones allow up to 731. Dependency and historical workday calculations scan at most 3,661 dates. Class-session searches allow 366 dates and 200 sessions. Time-zone tools use browser IANA rules and require a choice when local times repeat. Dates and policy rules are entered manually; no employer, retailer, school or local weather policy is inferred. Copy, CSV and printing include the calculation rules; calendar exports appear when the result contains dated events.
What happens to my dates?
Calculations run on your device. Saving a calculation is optional and keeps it in this browser. A setup link contains the dates and settings you entered; anyone with the link can read them. Use one tab per saved calculator. Clear saved data from Privacy & settings.