Duration estimates

Duration estimates provide information on the amount of time it will take to complete project work. They can be determined by developing an estimate for each activity, work package, or control account, using expert judgment or a quantitative method, such as:

  • Parametric estimating
  • Analogous estimating
  • Three-point estimating

For those activity durations driven by human resources, as opposed to material or equipment, the duration estimates will generally convert the estimate of effort hours into days or weeks. To convert effort hours into days, take the total number of hours and divide by 8. To convert to weeks, take the total number of hours and divide by 40.

Duration estimates include at least:

  • ID
  • Activity description
  • Effort hours

Duration estimates can receive information from:

  • Assumption log
  • Scope baseline
  • Schedule management plan
  • Activity list
  • Activity attributes
  • Milestone list
  • Resource requirements
  • Resource breakdown structure
  • Resource calendars
  • Project team assignments
  • Resource breakdown structure
  • Risk register
  • Lessons learned register

It provides information to:

  • Schedule baseline
  • Project schedule
  • Risk register

Duration estimates are an output from process 6.4 Estimate Activity Durations in the PMBOK® Guide – Sixth Edition. They are developed throughout the project as schedule and activity details are refined.

Tailoring tips

Consider the following tips to help tailor the duration estimates to meet your needs:

  • Duration estimates may include contingency reserve to account for risks related to uncertainty in the duration estimates, ambiguity in the scope, or resource availability.
  • Duration estimates at the level of accuracy that suits your project needs. Rolling wave planning is often used for duration estimating; as more information is known about the project activities, duration estimates are refined and updated.
  • For projects that are using an agile development approach, set time boxes are used rather than duration estimates. Additionally, different estimating methods are used.


The duration estimates should be aligned and consistent with the following documents:

  • Assumption log
  • Activity attributes
  • Resource requirements


Document element Description 
ID Unique identifier
Activity description A description of the work that needs to be done
Effort hours The amount of labor it will take to accomplish the work; usually shown in hours, but may be shown in days
Duration estimates The length of time it will take to accomplish the work; usually shown in days, but may be shown in weeks or months