Hints and Tips

Estimating Task Costs and Durations

The most accurate form of estimating is ‘bottom up’. Using this method a project is broken down into separate tasks of perhaps one or two days duration. The time requirement is estimated for each task (and costs and materials if this is required) and the individual estimates summed to give an estimate for the entire project. This method may be time consuming but it also has some additional advantages:

  • It forces the planner to analyse the project at a fairly detailed level and perhaps identify issues that might not otherwise have been anticipated.

  • It allows meaningful discussions on expenditure to take place with the project sponsor. If some parts of the project appear to be relatively expensive in relation to their value to the organisation they may be discarded or modified.

Project estimates are likely to be more accurate when team members have worked on similar projects before. If the work is of an unfamiliar nature you can use a variant of the jelly beans in the jar method referred to above:

  • Each member of the project team estimates a task without reference to other members of the team.

  • The estimates are reviewed and, if there are significant differences, team members explain the assumptions on which their estimates are based and repeat the exercise.

  • The estimates of all team members are averaged to give an overall estimate for the task.

Remember to add 10% contingency to your estimates to allow for unanticipated problems. It is better to complete a task early against a slightly more extended deadline than to be late against a shorter deadline.

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