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When you create a task in Project for the web, three things work together to determine the length of time it will take: effort, duration, and assignments. All Project for the web tasks are of fixed duration, and both changes to both duration and assignments alter the amount of effort for at task. 

Here's how it works in a little more detail: 

  • Effort: The amount of hours a group member or resource spends on a task. You can enter whatever amount of effort you like in the equation "Completed + Remaining = Total." After that, if you change duration or assignment, effort will adjust to fit. If a day is added to duration, effort is increased by one day's worth of hours.


    • Project does not assume that 1 day = 8 hours. A day's worth of effort is whatever you set it to be.

    • You can enter effort in hours, months, minutes, or weeks. However, all of these will be converted to display in hours.

  • Duration: The span of working time for a task, for example 2 days or 3 weeks. Duration is never affected by changes in effort and assignment. When you set your task to a duration of 2 weeks, you can add effort and the per-day hours will just increase, not the amount of days. When you assign an additional group member, the amount of hours per day will increase by another person, but the amount of days will stay the same unless you change it. 

  • Note: If you add Start and Finish dates before you add Duration, Project will fill in the duration based on these dates. If you add Duration before you add Start and Finish dates, Project will use the project Start date as the Start date of your task, and set the Finish date based on the Duration you entered. 

  • Assignment: Assigning a task to one group member will not affect either effort or duration. However, when you assign a task to 2 people, while the duration will stay the same the effort for that task will double. This is because Project assumes when you add a second resource you have another set of the same amount of work for that second person. If you meant to shorten duration by adding a second assignee, you will need to do that by reducing duration, and you'll have to reduce the hours as well.

Here's an example: If you have a task that you'll be working on for 2 hours a day, and you know it will take 8 hours to complete. You set the duration to 4 days, and the total effort to 8 hours. If you change the duration of that task to 5 days, Project will assume you are adding another 2 hours of effort, and total effort will now read 10 hours. 

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