Tuesday, June 2, 2009

Estimating Time Accurately

Accurate time estimation is a skill essential to good project management. It is important to get time estimates right for two main reasons:
  • Time estimates drive the setting of deadlines for delivery of projects, and hence peoples' assessments of your reliability
  • They often determine the pricing of contracts and hence their profitability.

Usually people vastly underestimate the amount of time needed to implement projects. This is true particularly when they are not familiar with the task to be carried out. They forget to take into account unexpected events or unscheduled high priority work. People also often simply fail to allow for the full complexity involved with a job.

Once you have a detailed list of all the tasks that you must achieve, make your best guess at how long each task will take to complete. Ensure that within your estimate you also allow time for project management, detailed project planning, liaison with outside bodies, meetings, quality assurance and any supporting documentation necessary.

Also make sure that you have allowed time for:
  • Other high urgency tasks to be carried out which will have priority over this one
  • Accidents and emergencies
  • Internal meetings
  • Holidays and sickness in essential staff
  • Contact with other customers, perhaps to arrange the next job
  • Breakdowns in equipment
  • Missed deliveries by suppliers
  • Interruptions
  • Quality control rejections

These factors may double (or more than double) the length of time needed to complete a project.

If the accuracy of time estimates is critical, you may find it effective to develop a systematic approach to including these factors. If possible, base this on past experience.