Scheduling
Part of Project scheduling and dependencies
Planning a critical path in project software
Enter real task relationships and durations, read float correctly and check why software marks a path as critical.
To plan a critical path, enter the activities, their durations and the relationships that control their sequence. Set the working calendar, calculate the schedule and inspect the path that drives the forecast finish. Check the logic and the software's critical-task settings before treating a highlighted path as a delivery commitment.
Create a network the software can calculate
Start with a defined finish milestone: what must be complete for the project to count as finished? Work backwards to identify the activities needed to reach it, then record each activity’s predecessor. A finish-to-start link suits work that must wait for an earlier task to finish. Leave independent work parallel.
Ask task owners for duration estimates and specify whether they are working days, elapsed days or another unit. Set the relevant calendar. A task lasting two working days does not necessarily finish two calendar days after it starts. Record external waits and date constraints separately from work duration so the resulting path can be explained.
Before calculating, check for missing and unnecessary links. A task with no predecessor may be independent or may be missing a handover. A long chain may reflect real sequence or merely the order in which someone entered the tasks. Either error can change the calculated path.
Steps to Plan a Critical Path in Project Software
- Define the project finish milestoneIdentify the final deliverable or completion point that marks project success.
- Work backwards to identify required activitiesMap out all tasks needed to reach the finish milestone, including dependencies.
- Record predecessor relationshipsUse finish-to-start links for sequential work; keep independent tasks parallel.
- Enter duration estimates and calendar settingsSpecify working days, elapsed days, or other units; apply the correct working calendar.
- Validate task links and durationsCheck for missing or unnecessary predecessors; ensure logical flow and accuracy.
Read the path, not just the colour
Consider this hypothetical network on one working calendar, with finish-to-start links, no resource limits and no date constraints:
| Route to the finish | Durations | Total |
|---|---|---|
| A → B → D | 2 + 3 + 2 working days | 7 working days |
| A → C → D | 2 + 2 + 2 working days | 6 working days |
B and C run in parallel after A, and D waits for both. The route through B determines the earliest finish at seven working days. C can slip one working day without moving D or the project finish. If B takes one additional working day, the earliest finish becomes eight working days, assuming nothing else changes.
That one-day allowance is total float for C in this simple network: the time it can slip before the project finish moves. It is also C's free float here because D is its immediate successor and cannot start until B finishes.
In a larger network, free float and total float can differ. Free float measures delay before a successor's earliest start moves; total float measures delay before the project finish moves.
Total Float vs Free Float in Project Scheduling
- Total FloatThe amount of time a task can be delayed without affecting the project's final finish date.
- Free FloatThe amount of time a task can be delayed without affecting the earliest start date of its immediate successor.
Check why a task appears critical
In an unconstrained network, activities with zero total float form a driving path. A software highlight can depend on the calculation rules and display settings. Check the task record and settings before telling the team why a task appears critical.
An unexpected path may also point to a wrong duration or a missing or unnecessary predecessor. Review it after a material delay or approved schedule change: another branch can become the driving route. Check whether the people and equipment assumed by the calculation will be available. Critical-path arithmetic alone does not settle resource conflicts.
Pros and Cons of Relying on Software to Highlight Critical Tasks
- ProsAutomatically identifies driving path based on logic and durations; improves consistency across projects.
- ConsMay highlight incorrect paths due to wrong inputs, missing constraints, or resource conflicts; does not account for availability of people or equipment.
Use the result to make a decision
For each driving activity, name its owner, remaining work, next dependency and date at risk. If the finish must improve, consider whether work can genuinely overlap, whether scope can change or whether more capacity would help. Record the cost and risk before changing a link; deleting a real prerequisite only makes the chart look faster.
Keep the baseline finish and current forecast visible together. When the path changes, explain which estimate, link or constraint changed and how that affected the forecast.
Key Metrics in Critical Path Analysis
- Project Finish Date (Baseline)
- To be determined by initial schedule calculation
- Current Forecast Finish
- Updated after delays or scope changes
- Zero Total Float Tasks
- Indicates critical path activities requiring close monitoring
