About PERT Chart Generator

Generate PERT charts for project planning with optimistic, pessimistic, and expected times. Part of the DevTools Surf developer suite. Browse more tools in the Diagrams & Workflows collection.

Use Cases

• Estimate a software project timeline with explicit optimistic, expected, and pessimistic scenarios.
• Calculate the probability of completing a project by a target date using PERT's statistical model.
• Identify the critical path in a project network to focus risk mitigation efforts.
• Compare PERT schedule estimates against a simpler Gantt chart estimate to quantify schedule uncertainty.

Tips

• Always define all three time estimates (optimistic, most likely, pessimistic) per task — PERT's value over simple scheduling is in the probabilistic duration modeling.
• Identify the critical path before presenting to stakeholders — tasks on the critical path have zero float and any delay directly extends the project end date.
• Use the standard deviation output (σ = (pessimistic - optimistic) / 6) to quantify schedule risk — high-σ tasks need contingency plans.

Fun Facts

• PERT (Program Evaluation and Review Technique) was developed by the US Navy and Booz Allen Hamilton in 1957 for the Polaris submarine missile program. It helped reduce the project's estimated completion time by 2 years.
• PERT uses a beta distribution to model task durations: Expected time = (O + 4M + P) / 6, where O=optimistic, M=most likely, P=pessimistic. The 4x weight on the most likely estimate reflects the beta distribution's central tendency.
• CPM (Critical Path Method) was developed independently by DuPont in 1957, also using a network diagram. Unlike PERT, CPM uses single-point (deterministic) duration estimates. Today, most project management tools blend both approaches.

FAQ

What's the difference between PERT and Gantt charts?

Gantt charts show tasks on a timeline with fixed durations. PERT charts show task dependencies as a network and model duration uncertainty using three-point estimates. They serve different audiences: Gantt for progress tracking, PERT for schedule risk analysis.

How is the critical path determined?

Forward pass: earliest start/finish for each task. Backward pass: latest start/finish to meet the project deadline. Tasks with zero float (ES=LS, EF=LF) are on the critical path.

Does it calculate schedule probability?

Yes — using the PERT formula for expected duration and variance, it calculates the probability of completing the project by a specified date using the normal distribution of the critical path's summed variance.