Critical Path and Project Slack Calculator
Calculate earliest and latest task times, total slack and critical tasks in a dependency network.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Topologically order the dependency graph. Run a forward pass for earliest starts and finishes, then a backward pass from the earliest project finish to obtain latest times and total slack.
ES=max(predecessor EF); EF=ES+duration; LF=min(successor LS); LS=LF−duration; slack=LS−ES
Worked example
A=3, B=4 after A, C=2 after A, D=1 after B and C finishes in 8 days. A, B and D are critical; C has 2 days of total slack.
Assumptions and input details
1–50 tasks; durations are nonnegative. Names are unique and contain no comma, hyphen or |. Dependencies are finish-to-start with zero lag, and cycles are rejected. Multiple independent starts and finishes are permitted. Critical tasks can form multiple paths; the result lists tasks, not an exhaustive path enumeration. No resource leveling, calendars, weekends or uncertain durations.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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