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12 Basic Rules for Estimating your Project

Estimates are required, to varying degrees of accuracy, at all stages of the project life cycle. The estimate is a crucial part of the project process, and the key to producing a good estimate, is quality of information. Various estimating techniques can be used but here we have concentrated on a summary of 12 basic rules which should be followed when estimating your project:

  1. Remember to estimate labour, materials, equipment and financial resources.
  2. Assume that labour resources will only be productive for 80 per cent of their time.
  3. Labour resources working on multiple projects take longer to complete tasks because of time lost switching between them.
  4. People are generally optimistic and often underestimate how long tasks will take.
  5. Make use of other people’s experience and your own.
  6. Obtain an expert view.
  7. Include management time in any estimate.
  8. Always build in contingency for problem solving, meetings and other unexpected events.
  9. Cost each task in the work breakdown structure to arrive at a total, rather than trying to cost the project as whole.
  10. Agree a tolerance with your customer for additional work that is not yet defined.
  11. Communicate any assumptions, exclusions or constraints you have to your customer.
  12. Provide regular budget statements to your customer, copying your team, so that they are always aware of the situation.


  • Not understanding what is involved to complete an item of work.
  • Starting with an amount of money and making the project cost fit.
  • Assigning resources at more than 80 per cent utilisation.
  • Failing to build in contingency.
  • Failing to adjust the estimate in accordance with changes in scope.
  • Dividing tasks between more than one resource.
  • Providing estimates under pressure in project meetings.