Duration Estimating Worksheet
Calculate activity durations using parametric, analogous, and three-point (PERT) estimating techniques to build a realistic schedule baseline.
In this resource
§1 Purpose of the Estimating Worksheet
This worksheet documents the mathematical and historical basis for your schedule duration estimates, providing transparency into how timelines are calculated.
Project managers rarely rely on a single estimating method. Instead, they apply different techniques depending on the nature of the work and the historical data available. By documenting the exact parameters, multipliers, and PERT weightings used, the PM defends the schedule against arbitrary cuts and ensures the estimates can be independently validated.
- Parametric: Statistical scaling (e.g., 4 hours per page × 10 pages).
- Analogous: Historical comparison (e.g., "The last server migration took 5 days").
- Three-Point (PERT): Weighted average of Optimistic, Pessimistic, and Most Likely outcomes to manage high-uncertainty tasks.
§2 Blank Template
A structured format to break down the calculations for each estimating method.
DURATION ESTIMATING WORKSHEET
This worksheet documents the basis of duration estimates for the project. Three estimating techniques are used: parametric, analogous, and three-point (PERT).
Parametric Estimates
Formula: Duration = Effort ÷ (Resources × Hours/day × %Available × Performance Factor).
| ID | Effort Hours | Resource Quantity | % Available | Performance Factor | Duration Estimate |
|---|---|---|---|---|---|
| [ID] | [Hrs] | [Role/Count] | [%] | [1.0] | [Days] |
Analogous Estimates
Used when reliable history exists. Multiplier accounts for differences in scope, complexity, or team size.
| ID | Previous Activity | Previous Duration | Current Activity | Multiplier | Duration Estimate |
|---|---|---|---|---|---|
| [ID] | [Historical Task] | [Days] | [Current Task] | [1.0] | [Days] |
Three-Point (PERT) Estimates
PERT (beta) weighting: tE = (O + 4M + P) / 6. Used for activities with significant uncertainty.
| ID | Optimistic (O) | Most Likely (M) | Pessimistic (P) | Equation | Expected Duration |
|---|---|---|---|---|---|
| [ID] | [Days] | [Days] | [Days] | (O + 4M + P) / 6 | [Days] |
§3 Worked Example: Mary's Consulting
A completed example demonstrating how a PM calculates and justifies duration timelines across a mix of highly predictable and highly uncertain tasks.
DURATION ESTIMATING WORKSHEET
This worksheet documents the basis of duration estimates for the project. Three estimating techniques are used: parametric, analogous, and three-point (PERT).
Parametric Estimates
Formula: Duration = Effort ÷ (Resources × Hours/day × %Available × Performance Factor).
| ID | Effort Hours | Resource Quantity | % Available | Performance Factor | Duration Estimate |
|---|---|---|---|---|---|
| A006 | 30 hrs | 1 PM | 75% | 1.0 | 5 days |
| A014 | 100 hrs | 1 writer | 70% | 1.0 | 18 days |
| A016 | 60 hrs | 1 writer | 30% (waiting) | 0.5 | 25 days |
Analogous Estimates
Used when reliable history exists. Multiplier accounts for differences in scope, complexity, or team size.
| ID | Previous Activity | Previous Duration | Current Activity | Multiplier | Duration Estimate |
|---|---|---|---|---|---|
| A001 | Charter (prior internal project) | 5 days | Develop Project Charter | 1.0 | 5 days |
| A011 | Brand refresh (prior project) | 12 days | Develop Visual / Brand Design | 1.25 | 15 days |
| A039 | Prior site launch hypercare | 10 days | Post-Launch Hypercare | 1.0 | 10 days |
Three-Point (PERT) Estimates
PERT (beta) weighting: tE = (O + 4M + P) / 6. Used for activities with significant uncertainty.
| ID | Optimistic (O) | Most Likely (M) | Pessimistic (P) | Equation | Expected Duration |
|---|---|---|---|---|---|
| A009 | 3 | 5 | 9 | (O + 4M + P) / 6 | 5.3 → 5 days |
| A024 | 12 | 15 | 22 | (O + 4M + P) / 6 | 15.7 → 16 days |
| A032 | 5 | 8 | 14 | (O + 4M + P) / 6 | 8.5 → 8 days |
Fractional Availability
Observe A016 (Parametric). The writer only has 60 hours of active effort, but is waiting on 500+ consultants to reply. By setting "% Available" to 30%, the PM mathematically defends extending the duration to 25 days.
Multiplier Adjustment
In A011 (Analogous), the historical brand refresh took 12 days. However, the PM recognises the current project is more complex and applies a 1.25 multiplier to safely estimate 15 days.
PERT Weighting
The PERT formula uses a "Beta" distribution. By multiplying the Most Likely (M) estimate by 4, it heavily weights the average toward reality while still absorbing the outlier risk of the Pessimistic (P) scenario.
Handbook application: from concept to controlled practice
Purpose. This expanded section turns the original page into a practical handbook. It preserves the supplied material and adds a repeatable way to apply, check and review Duration Estimating Worksheet. It does not replace a contract, legislation, a controlled standard, competent engineering judgement or specialist advice.
The operating aim is to make the blank artefact usable by explaining what belongs in each field, who supplies it and how it is reviewed. Read the original explanation first, then use the workflow and checks below to convert knowledge into evidence.
Use Duration Estimating Worksheet as a decision instrument rather than an administrative form. The subject terms—estimating, worksheet, duration, template, example—need an explicit connection to the project objective, business value and stakeholder commitments. Before completing the artefact, write one sentence stating who will use it, what decision it supports and when that decision is required.
Apply a disciplined information model. Separate facts supported by evidence, forecasts derived from a method, assumptions awaiting validation, constraints that limit choice, risks that may occur, issues that already exist and actions assigned to people. Each material entry should have an owner, date, status and next review point. Where probability or impact scores are used, define the scale so different reviewers interpret it consistently.
A baseline is useful only when changes are visible. Give the artefact an identifier, version, approval state and effective date. Define which changes require reapproval, how superseded versions are retained and where supporting evidence is stored. During reviews, focus on exceptions, decisions and trends rather than reading every field aloud. Record the decision and rationale, not merely that a meeting occurred.
Close the loop beyond delivery. Confirm acceptance criteria, unresolved items, transferred responsibilities and operational ownership. Where benefits are expected, identify the outcome measure, baseline, target, observation period and owner who remains accountable after the project team disbands. Lessons should describe the condition, consequence and reusable action; a generic statement such as “communicate better” cannot improve the next project.
Step-by-step operating method
- Name the decision. Write the decision, approval, handover or control activity the completed template must support.
- Assign ownership. Nominate one accountable owner and identify contributors, reviewers and approvers.
- Gather evidence. Use records, estimates, stakeholder input and source references rather than unsupported opinion.
- Complete with discipline. Use consistent dates, units, identifiers, status values and version controls.
- Review and maintain. Check completeness and logic, approve the baseline, then update it when trigger conditions occur.
Completion and governance protocol
Start with a short drafting workshop involving the accountable owner and the people who hold the evidence. Complete high-consequence fields first: objective, scope, owner, baseline, acceptance, dependencies and escalation. Mark unknowns as assumptions or actions rather than hiding them behind vague prose. Circulate a review draft, resolve conflicting interpretations, baseline the approved version and place the next review date in an owned schedule.
| Information type | Minimum useful content | Review test |
|---|---|---|
| Outcome | Observable change and intended recipient | Not merely a deliverable or activity |
| Measure | Definition, baseline, target, frequency and source | Two reviewers would calculate it the same way |
| Ownership | One accountable role plus contributors and approver | Authority matches responsibility |
| Uncertainty | Assumption, risk or issue with response and trigger | Status reflects current reality |
| Control | Version, approval, review date and change rule | Current baseline is identifiable |
Common failure modes and recovery actions
1. Watch for
Filling every box even when a field is not applicable instead of recording why.
Recovery: Return to the governing definition or requirement and restate the decision in one sentence.
2. Watch for
Writing vague statements without an owner, measure, date or evidence source.
Recovery: Separate evidence from assumption, assign an owner and set a date for validation.
3. Watch for
Copying a previous project without revalidating assumptions and stakeholders.
Recovery: Run a small counterexample, boundary test, pilot or independent check before proceeding.
4. Watch for
Using the document as a private worksheet when it is meant to support a shared decision.
Recovery: Record the consequence, decision and rationale, then update the controlled baseline.
5. Watch for
Creating an approved baseline but failing to define who maintains it and when.
Recovery: Escalate when the issue affects safety, compliance, acceptance, material value or an agreed tolerance.
Review checklist
- Is the purpose and intended decision clear to a reader outside the team?
- Are owners, dates, measures and sources complete and internally consistent?
- Which fields are assumptions and how will they be validated?
- What event, threshold or review date causes this document to change?
- Are mandatory requirements distinguished from recommendations and illustrative values?
- Are sources, assumptions, units, dates and versions recorded closely enough to reproduce the decision?
- Have safety, legal, ethical, stakeholder and operational consequences been considered at the appropriate level?
- Is there a named owner and a trigger for review, escalation, change or retirement?
Questions for deeper application
What is the most important distinction a practitioner must preserve when applying Duration Estimating Worksheet?
Answer with a fact or cited source where available. Where evidence is incomplete, record the assumption, consequence, responsible owner and next validation action.
Which assumption about estimating would change the result most if it proved false?
Answer with a fact or cited source where available. Where evidence is incomplete, record the assumption, consequence, responsible owner and next validation action.
What evidence would allow an independent reviewer to reproduce or challenge the conclusion?
Answer with a fact or cited source where available. Where evidence is incomplete, record the assumption, consequence, responsible owner and next validation action.
Which boundary, exception or failure case has not yet been tested?
Answer with a fact or cited source where available. Where evidence is incomplete, record the assumption, consequence, responsible owner and next validation action.
What must be handed over, monitored or reviewed after the immediate work is complete?
Answer with a fact or cited source where available. Where evidence is incomplete, record the assumption, consequence, responsible owner and next validation action.
Authoritative references and use notes
The sources below were selected as institutional or primary guidance for the broader practice. They support the handbook method; they do not imply that every statement or clause in a source applies to every project. Confirm the current edition, jurisdiction, contract and application before treating any requirement as mandatory.
- PMI Standards and Publications — Project Management Institute. Used for project, program, portfolio and organisational project management. Accessed 2026-08-13.
- ISO 31000 family — Risk management — International Organization for Standardization. Used for principles and guidance for enterprise risk management. Accessed 2026-08-13.