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How to add task duration to a Project Schedule

This is a guide to project planning covering 4 steps. If you haven't read steps 1 - 2 or 4, you can access them here. Stage 1 - Work Breakdown Structures, Stage 2 - Precedence Diagrams, Stage 4 - resource allocation and levelling

In this 3rd stage of project planning you estimate the duration needed to complete each task, and you finally get to use your project planning software!

Estimating Task Duration

You can either estimate task duration with your project team or you can get the estimates separately from your team after you have created the Work Breakdown Structure (WBS) and Precedence or Workflow diagram. In a group session simply go through your work flow diagram or project plan and ask your team to estimate the duration required for each task.

NOTE: Estimating is a specialist subject so for the moment lets assume that the experts in your project team are sufficiently informed to estimate the duration for their deliverables.

Duration Estimation Template

Develop Parametric, Analogous and Three-point estimates using this worksheet. Includes formulas for PERT Beta distribution and Triangular distribution.

Enter the task duration into your scheduling software, in Microsoft Project use the Duration column.

add task duration

You shouldn’t be setting start dates and finish dates for tasks. Why? If you are trying to force your project plan to meet pre-set dates you are already in big trouble. See common planning mistakes - fixing finish and start dates and Constraints - what they are used for and common mistakes

Once you have entered the task effort, your planning software will automatically calculate the start and finish date for each task and provided you have entered the project logic correctly it will calculate the critical path through the plan and return an accurate possible end date. In Microsoft Project simply set the project start date and let the program do the rest.

At this point the end date can only be achieved if sufficient resource is available. That is why it is only a possible end date. This will become clearer in stage 4 when we allocate resources to our plan.

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Project scheduling - the top 5 checks you need to make!

Now you have entered tasks, logic and effort into your project plan go through and look out for the following:
  1. Abandoned Tasks - tasks without predecessors or successors (tasks that don't link to any other tasks).
  2. Start or finish dates that have been manually entered. In MS Project these will show up as constraints. It is important to avoid fixing start and end dates because it prevents the accurate calculation of the Critical Path.
  3. Tasks scheduled over bank holidays, Easter or Christmas - make sure holidays are classed as non-working time.
  4. Blank task names. Check all tasks have clear descriptions that the team will understand.
  5. Tasks with default durations. MS project sets all new tasks to 1day? by default
Ok now you have checked your project plan it is time to move to stage 4 and allocate resources.