Most Likely Duration is the estimated time that an activity is expected to take under normal conditions, accounting for all known variables such as resources, complexity, and typical delays. It reflects the most realistic estimate, assuming that work proceeds as planned without major risks or accelerations.
Purpose and Characteristics
- Core of Triangular and Beta Distributions – Used in both basic and PERT-based estimating.
- Baseline for Planning – Often used as the default estimate in deterministic schedules.
- Balanced Viewpoint – Unlike optimistic or pessimistic estimates, it assumes moderate risk and average performance.
Use in Estimating Techniques
Most likely duration is one of three estimates typically used in:
- Three-Point Estimating:
- Optimistic
- Most Likely
- Pessimistic
- Program Evaluation and Review Technique (PERT):
Where E is the expected duration, O is optimistic, M is most likely, and P is pessimistic.
Example Scenario
For a task like writing technical documentation, if everything goes as it usually does, the writer estimates it will take 5 days—that’s the most likely duration. However, it could take 3 days if everything goes smoothly, or 8 days if delays occur.
Mermaid Diagram: Role in Duration Estimation
flowchart LR A[Optimistic Estimate] --> D[Three-Point Estimating] B[Most Likely Estimate] --> D C[Pessimistic Estimate] --> D D --> E[Expected Duration]
Why Most Likely Duration Matters
- Improves Accuracy – Forms the anchor for expected value in probabilistic estimating.
- Balances Risk – Helps teams avoid overly aggressive or padded estimates.
- Integrates with Tools – Used in schedule simulations and forecasting models.
See also: Optimistic Duration, Pessimistic Duration, Three-Point Estimating, PERT.