Project Timeline Planner
Plan phases with durations and dependencies; auto-compute start, end, and project finish dates.
Written by Golam Rabbani, Founder & Lead Engineer
How to use this project timeline planner
- Enter a project start date in the "Project start date" field.
- Type a phase name and duration (in days) in the "Add a phase" section, then choose a dependency from the "Depends on" drop-down (or leave it as "None").
- Press "Add phase" to add it to the phase table; repeat for every phase.
- Reorder phases with the up/down arrows or edit names and durations inline in the table.
- Press "Compute timeline" to see each phase's start and end dates, then use "Copy" to copy the full timeline as plain text.
About this project timeline planner
The project timeline planner calculates the start and end date of every phase in a multi-phase project, chaining them together through their declared dependencies.
The tool works by resolving each phase in dependency order. A phase with no dependency starts on the project start date. Its end date is computed as start + (duration − 1) days, so a 10-day phase beginning on 2026-06-01 ends on 2026-06-10. A dependent phase begins the day after its predecessor ends. Phases that share no dependency chain can run from the same start date in parallel — the project end date is the latest end date across all phases. Before computing, the tool performs a cycle check: if phase A depends on B and B depends on A, the tool blocks the dependency and shows an error.
Worked example: start date 2026-06-01. Discovery (10 days, no dependency) runs 2026-06-01 to 2026-06-10. Design (14 days, depends on Discovery) runs 2026-06-11 to 2026-06-24. Build (30 days, depends on Design) runs 2026-06-25 to 2026-07-24. The project end date is 2026-07-24.
Your phase list and start date are saved automatically to your browser's localStorage, so you can close the tab and resume where you left off.
FAQ
- How are dependencies handled in the project timeline planner?
- Each phase can declare one predecessor in the "Depends on" field. When computing, the tool sets that phase's start to the day after its predecessor's end date. Phases with no dependency all start on the project start date.
- What happens if I create a circular dependency?
- The tool detects cycles before they are added. If the new dependency would create a loop — for example, phase A depending on B while B already depends on A — the "Add phase" step shows an error and the phase is not added. Inline dependency changes that would create a cycle are silently rejected.
- Do weekends or holidays affect the dates?
- No. The tool uses calendar days only. A 10-day phase spans 10 consecutive calendar days regardless of weekdays, weekends, or public holidays. If you want to account for working days only, increase the duration to reflect the actual calendar span.
- Does my plan save automatically?
- Yes. The start date and all phases are written to your browser's localStorage whenever you make a change. Your plan reloads automatically the next time you open the tool in the same browser. Clearing site data or using a private/incognito window will wipe the saved state.
- Can a phase depend on more than one predecessor?
- Each phase supports one predecessor in the current implementation. To model a phase that must wait for two earlier phases, set the dependency to whichever predecessor ends latest, or add an intermediate "sync" phase that follows both.
- Is the project timeline planner free to use?
- Yes, it is free with no account or sign-up required. All computation runs in your browser; no data is sent to a server.