Duration And Effort - Where Are the Differences?

Annalena Simonis, Thursday 11 March 2021 | Reading time: 3 min.

Caution: Don't get these terms mixed up! We are finally clearing up misunderstandings and errors around well-known project management terms. This week we explain the difference between duration and effort in a project.

One of the most common usage mistakes, which still leads to a number of misunderstandings in today's everyday project work, is the confusion between effort and duration. It is important to know the differences, especially when it comes to project planning. This article will help you to better distinguish between those two terms in the future and to avoid misunderstandings in the project team. We have listed the most important differences for you at a glance in the following table:

Duration vs. Effort
Total time to complete a project or task. vs. Actual work time for a project task.
Measured in working days, hours or weeks. vs Measured in man-hours, -days or -weeks measured.


In summary, duration describes the entire period between the official start of the project and the end of the project, as well as the time planned for the completion of a single task. The effort, on the other hand, describes the actual working hours that an employee spends on this task. In a business sense, effort has other meanings besides the measurement of person-hours. In a company, effort is a value that also measures the amount of money and materials consumed, which is why it is also referred to as effort costs (wages, office supplies, operating materials).

The difference between duration and effort becomes even clearer with the following example:
Projects that we are all familiar with often take place at home. So, let's assume you want to paint several rooms in your apartment.

  • You estimate that it will take you about 20 active hours of work. Unless you plan to paint your walls 20 hours at a time without a break, you will spread the hours of work over several days. For example, if you have 5 hours a day to paint your home, you would finish the job in 4 days (20 hours total divided by 5 hours/day).
  • With the help of another person who also paints your apartment for 5 hours a day, the duration of the project is halved since two resources each invest 5 hours a day in the task. Your walls will then be finished in two days (20 hours total effort divided by 10 hours/day).
  • However, if the person helping only has 3 hours per day, the project will take 2.5 days because you both will only work a total of 8 hours per day (20 hours total effort divided by 8 hours/day).
  • Conclusion: The effort of the project "Paint the apartment" always remains the same no matter how many helpers you have. Only the total duration can be shortened by the increased use of resources.

The situation is different when the duration of a project is fixed. Imagine your company is participating in a trade fair. It has a pre-defined start and end date. For this period, your marketing department schedules an employee for stand support. At short notice, another colleague is assigned to assist. Despite the increased use of resources, the effort is doubled instead of being halved because two employees are now at the trade fair stand for several days at the same time. The duration of the project will not change as it is fixed.

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