Estimating a project deadline can be a difficult task for anyone trying to factor in unforeseen obstacles. Should your estimate be closer to the best or worst case scenario? Obviously, the client wants their project done quickly and while this may pad your bank account in the short term, if the project ends up over time and over budget your name could be tarnished.

Bert Webb shows us one way of estimating realistic project deadlines by breaking down the estimate into an equation. A reasonable prediction is determined by running optimistic, pessimistic, and realistic time frames through a formula developed by Snead and Wycoff.


>- Te = Realistic time estimate - To = Most optimistic time estimate (the Sunny Side estimate with no setbacks) - Tp = Most pessimistic time estimate (with every obstacle happening) - Tm = Most probable time estimate (this makes you think realistically; some setbacks happen, others don’t)

>Let’s say we have a project of developing a departmental newsletter. The variables break down as follows:

>- Tm = 14 days - To = 10 days - Tp = 30 days

>The calculation would be:

>Te = (10+(4X14)+30)/6

>The best estimated duration for the project would be 16 days.

Give it a try to see if your estimates are where they should be.

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Kevin Hale

Estimating Project Deadlines by Kevin Hale

This entry was posted 5 years ago and was filed under Notebooks.
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  1. Brian Benzinger · 5 years ago

    That is genious. Perfect. I am going to try this on my next big project and see how it goes. Thanks bringing that article to my attention. And all this time I always guessed =p

  2. Adrian Trenholm · 5 years ago

    You can also use an average of optimistic, pessimistic and probable:

    Te=(To + Tm + Tp)/3


    Te = (10 + 14 + 30)/3 Te = 18

    The Snead and Wycoff formula puts weight on the probable, whereas a straight average puts a bit more weight on the pessimistic (or at least it does if you are being properly pessimistic).

    If your probables are usually reasonably accurate, then use Snead and Wycoff; if you are consistently going over your estimated deadline, then switch to the average method.