Interactive tool
Critical path calculator
Type your activities, durations and finish-to-start predecessors. The forward pass, backward pass, total float and critical path recalculate on every keystroke — no sign-up, nothing leaves your browser. It loads with the 9-task website migration example from the Gantt vs critical path guide so you can experiment before entering your own schedule.
1. Your task list
| Code | Task | Duration (days) | Predecessors | Remove |
|---|---|---|---|---|
Schedule summary
Project duration
33days
Critical path
A → B → C → E → H → I
3 of 9 tasks carry float and can slip without moving the finish date.
2. Forward pass, backward pass and float
| Task | Dur | ES | EF | LS | LF | Float | Critical |
|---|---|---|---|---|---|---|---|
| AContent audit | 5 | 0 | 5 | 0 | 5 | 0 | Critical |
| BInformation architecture | 4 | 5 | 9 | 5 | 9 | 0 | Critical |
| CVisual design | 8 | 9 | 17 | 9 | 17 | 0 | Critical |
| DContent rewrite | 10 | 9 | 19 | 12 | 22 | 3 | slack 3d |
| EFront-end build | 9 | 17 | 26 | 17 | 26 | 0 | Critical |
| FCMS setup & data model | 6 | 9 | 15 | 16 | 22 | 7 | slack 7d |
| GContent load | 4 | 19 | 23 | 22 | 26 | 3 | slack 3d |
| HIntegration & QA | 5 | 26 | 31 | 26 | 31 | 0 | Critical |
| ICutover & DNS switch | 2 | 31 | 33 | 31 | 33 | 0 | Critical |
3. Schedule view
Solid bars are the early schedule. The lighter tail shows available float.
- A Content auditd0–5
- B Information architectured5–9
- C Visual designd9–17
- D Content rewrited9–19
- E Front-end buildd17–26
- F CMS setup & data modeld9–15
- G Content loadd19–23
- H Integration & QAd26–31
- I Cutover & DNS switchd31–33
How to read the numbers
- ES / EF (early start, early finish)
- The soonest a task can start and finish once every predecessor is done. Day 0 is the project start.
- LS / LF (late start, late finish)
- The latest a task can start and finish without pushing the project completion date.
- Total float
- LS minus ES — how much a task can slip before it starts costing the project. Zero float means the task is on the critical path.
Related guides
Go deeper on the scheduling maths this calculator runs.
- People & DeliveryStakeholder Management: The 4-Quadrant Grid That WorksMapping power and interest, then engineering the information flow that keeps a project unblocked. 6 min read
- PlanningHow to Find the Critical Path (In 4 Simple Steps)How to find the sequence that actually determines your end date — and what to do about it. 8 min read
- PlanningTotal Float vs Free Float: Formulas + Worked ExampleTotal float protects the project end date; free float protects the next task. Worked numbers showing why confusing the two costs you weeks. 7 min read