Time. It’s all any of us ever want. More time. We are never happy with the time we have; it’s never enough, is it? Time is one unique, non-renewable resource that is irreplaceable. But we make do with what we have. We learn to manage time. In the words of Peter F. Drucker, “Until we manage time, we can manage nothing else.”

Time estimation and management can make or break a project and is therefore critically important in the Project Management field.

It’s important to estimate time correctly, for two main reasons:

  1. Deadlines for project planning and delivery come from the estimated duration. Poor estimation results in drawn-out, lengthy delivery, and turnaround times, which can not only affect the company’s bottom line but can also cause questions about your competence and reliability as a project manager. It’s important to estimate time correctly, for two main reasons:
  2. Deadlines also regulate contract pricing—which can affect the profitability of the project or contract.

Scheduled activities in the “Estimate Activity Duration” phase of a project are prioritized using these three factors:

  • Effort
  • Duration
  • Time Elapsed

In this article we will cover the following topics in detail: 

  • What is the effort?
  • What is duration?
  • What is elapsed time?

The effort is the number of units of work performed. The duration of a project is the amount of time that must be spent based upon the effort and the resources available (excluding holidays and non-working days). The elapsed time is calculated according to the calendar (including holidays and non-working days).

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What is the Effort?

As the name suggests, “effort” is defined as the amount of work, or the number of work units used to complete an activity. In simple terms, the effort is the number of hours workers spend, focused on a particular task, to get a certain job done. If you want to determine the other two, you must first determine the effort in a project. The effort is most often expressed in staff hours, days, or weeks.

Stakeholders often want to know how much a project will cost. This chiefly depends on the measure of time members of the project spend on the project. A simple example to explain this concept follows. Let’s say you begin to paint your house. You work for 6 hours a day for 9 days. Your effort would then be the amount of time you take in a day multiplied by the number of days you work, which would be 54 hours. The effort you put in is 54 hours.

What is Duration?

Duration is defined as the entire time taken to complete an activity, based on the resources allocated to the project. It stretches from when the task first began to the day it ended and does not include time off like holidays or other non-working days. It is also referred to as calendar time.

The duration can be expressed in Work Hours, Work Days, and Work Weeks.

Take the same example given for effort. You begin to paint your living room. You work for 6 hours a day for 3 days. The time duration of your work painting the living room is 3 days.

What is Elapsed Time?

Elapsed time is the time between designating a resource to a task and the completion of the task. In simple terms, it is the passage of calendar days. Elapsed Time includes holidays and weekends. Elapsed time can be traced by milestones that have been set on the schedule of the project.

Consider the first house painting example. You work for 6 hours a day for 9 days. The elapsed time for a normal day’s work maybe 4 hours, which includes 4 hours of real-time work plus breaks and lunchtime. Your Elapsed Time is 11 days, and that includes a Saturday and a Sunday, including the breaks you take in between.

Another example: you work on a construction project for eight days from Monday to the next Wednesday, with a weekend (Saturday and Sunday) in between. Your elapsed time is 10 days since the non-working days are also counted.

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In the Project Management Exams

The effort, Duration, and Elapsed Time constitute a small part of the Time Management/Scheduling Module. You may not get questions about these during your own exam, but it is important for you to understand these concepts. 

As a project manager, you should be well-trained in Project Time Management to be able to effectively manage deadlines and other time constraints. Without this skill, the project you are running can head straight down the hill, accumulating increased overheads.

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The table below compares and contrasts the three concepts covered in this article.

  Effort Duration Elapsed Time
Definition The number of work units that is vital to complete an activity The entire time is taken to complete an activity The time between designating a resource to a task and completing the task
How it is measured Staff - hours, days or weeks Work Hours, Work Days and Work Weeks
(not including weekends or holidays)
Work Hours, Work Days and Work Weeks
(including weekends and holidays)
Example House Painting :
6 hours a day for 9 days:
Effort = 54 hours
House Painting :
6 hours a day for 3 days: Duration = 3 days
House Painting :
6 hours a day for 9 days: Elapsed Time = 11 days


If you’re studying for a project management exam like the PMP®, consider online Project Management training from Simplilearn. We offer a wide variety of project management courses designed to help you pass the PMP exam on the first try, taught by certified faculty with at least 10 years of industry experience.

Want a taste of Simplilearn training? Watch our video Introduction to PMP Certification Training.

PMP is a registered mark of the Project Management Institute, Inc.

About the Author

Avantika MonnappaAvantika Monnappa

A project management and digital marketing knowledge manager, Avantika’s area of interest is project design and analysis for digital marketing, data science, and analytics companies.

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