Duration versus effort

Duration and Effort are terms of central importance in project management. However, they are often misunderstood or used incorrectly. Especially when duration is equated with effort, the resulting project plans are not resilient to the delays and external influences that occur in day-to-day project management. Both terms refer to different aspects of the planning and execution of work packages and projects. A precise understanding of these terms is crucial for successful project planning and management.

Duration refers to the entire period from the start to the completion of a work package or project. It is usually measured in calendar days, weeks or months. Duration includes all periods of time spent working on the work package, as well as periods of time when work is interrupted due to external dependencies or other factors.

Effort, on the other hand, refers to the total amount of work required to complete a work package. Effort is measured in hours, days or other work units and only takes into account the active working time.

Duration and effort therefore refer to different aspects of the planning and execution of work packages and projects.

The definitions show a clear difference between duration and effort. Effort describes the estimated working time required to complete a project or work package and refers exclusively to the required working hours. Duration, on the other hand, indicates the period - in days, weeks or months - over which these working hours are to be distributed.

(Left: Effort 16 hours, duration 2 days; Middle: Effort 16 hours, duration 5 days; Right: Effort 16 hours, duration 8 days)

The effort per day therefore changes if the duration of a project or work package changes. This is because the total effort remains the same while the duration changes, so the effort is just distributed differently over the days. If the duration is shorter, the effort per day increases, as the same total effort has to be completed in a shorter period of time. If the period is longer, the effort per day decreases because the total effort can be spread over more days. There are either a few long bars or many short bars, but the sum of the bars is always the same. This is because the sum of the bars is the effort.

This is based on an 8-hour working day. Both terms therefore refer to specific time calculations in project management.

(Left: Effort 32 hours, duration 4 days; Right: Effort 32 hours, duration 2 days per person)

If more resources are available to manage the same effort, the duration can be shortened as the effort is distributed among the available resources. For example, if there are two people, the effort is divided between them. This means that each person has half the effort. Instead of scheduling 32 hours for one person, each person only has to spend 16 hours. The total effort is still 32 hours, but can be completed in less time. While one person working 8 hours per day requires 4 days, two people can complete 32 hours in 2 days. The total effort therefore remains the same, while the duration depends heavily on the number and availability of resources.

(Left: 16 hours, duration 3 days; right: 16 hours, duration 2 days with one day of vacation)

It can also happen that a work package has been calculated with an estimated effort of 16 hours and a planned duration of 3 days, but the person responsible is already scheduled for one day in another project or is on vacation on one day. In this case, the workload of 16 hours is distributed over the remaining days. As before, the total effort remains the same, only the distribution of working time changes according to the available working days.

Although both terms are clearly defined, duration and effort are closely linked and interdependent.

In project management, there are various best practices that relate to both effort and duration to ensure the smooth implementation of projects and work packages.

(Left: Effort 16 hours, duration 2 days; Right: Effort 16 hours, duration 4 days)

The duration of a work package is often set longer than the estimated effort required. This is to avoid delays that could otherwise lead to problems in other areas. Time buffers of 20% to 100% are often planned. For example, an effort of 16 hours (2 days) could be estimated to take 4 days. Higher allowances are also common in practice.

These buffers spread the effort over a longer period of time, which means that less work has to be done in one day to complete the effort in the set time. If delays occur, the effort is shifted to the available days in order to meet the deadline. The sum of the bars remains the same, only the size of the bars changes. In this way, it is possible to react more flexibly to delays without having to adjust the plan.

(Left: One work package, effort 16 hours, duration 4 days; Left: Two work packages divided between two people, effort 16 hours, duration 2 days)

If two people are responsible for a work package, the duration is halved in terms of calculation. In practice, however, it is often not possible for one person to take on exactly half of the work package. One possible solution is to divide up the work package so that it can be assigned to one person at a time. In this way, responsibility is also clearer and simultaneous processing of the same topic is avoided.

(Left: Several work packages that are planned one after the other; Right: Several work packages that are planned at the same time.)

Another frequently used method is the parallel assignment of several work packages to one person. The work packages are assigned such a long duration that individually they only lead to a low workload per day, but together they result in the desired target workload. This has the advantage that other work packages can be used in the event of delays in one work package. Delays can occur, for example, if feedback from the client is not received on time or colleagues are not available. It is not unusual for an employee to be assigned 3-4 or more work packages in parallel.

The workload of employees can only be planned realistically if the project planning software provides a clear and, above all, cross-project overview of resource utilization, makes conflicts visible and enables resources to be balanced efficiently.

Resource planning is calculated over a period of time in which the employee can act independently. If, in the example above, each of the four bars leads to a workload of 2 hours per day, this results in a total workload of 8 hours per day. This means that the employee's workload is within their target. The employee can then organize their work independently and flexibly within the specified framework and independently compensate for any delays in the work packages. The project manager does not have to constantly adjust the project plan and does not have to intervene as long as the four work packages are completed within the specified time frame. The responsibility for completing the work packages on time is therefore transferred to the employee. It must be possible for the project manager to monitor progress at any time.

In the Octaved Flow project management software, the duration and effort functions are implemented according to the usual conventions and as described above. Octaved Flow provides a clear, cross-project overview of resource utilization, identifies potential conflicts at an early stage and enables targeted and efficient balancing of resources. In many projects, employees are assigned to several work packages at the same time. Octaved Flow makes the workload of employees transparent and ensures that projects remain on schedule and within budget even in the event of unforeseen circumstances.

In addition to project planning, Octaved Flow also maps other project management processes, such as project controlling, KPIs, progress monitoring and the recording and billing of project times. Furthermore, Octaved Flow is able to calculate all changes to the project plan at all levels and thus helps to create a comprehensive and complete picture of the entire project portfolio.