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How To Correctly Sandbag Your Estimates

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How To Correctly Sandbag Your Estimates

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All to often I hear this phrase during an estimation meeting:

I think it’s about 20 hours, but let’s say 24 to fudge it a little…

Estimating this way brings a false sense of security that you have allotted more time than needed. Probably more correct, that small amount of extra hours placed on the estimation only shortened the gap between an optimistic timeline and reality. So why is this a poor estimation?

Single Point Estimations Stink

I have said this many times, and I will say it again - single point estimations stink. Sure you can tell the difference between a 1 hour task and a 2 hour task, but can you really tell the difference between a 20 hour task and a 24 hour task. Probably not.

Solution: Learn to break down your estimations in smaller pieces. For larger tasks, ensure you are estimating in ranges or with a process that implicitly includes a fudge factor such as Planning Poker (Point Estimation).

Fudge Factor Is Not Based On Fact

In the example above, where did the extra 4 hours come from? The majority of the time it is a gut feeling, but why can’t it be fact?

Solution: Keep track of your estimations and actual development time - you can’t fix what you can’t measure. Next, measure and understand your estimation variances. This will give you 2 action plans:

  1. You can correctly pad your estimates with actual mathematical variance to improve estimation confidence.
  2. You can now understand and measure estimation improvement (for example, 20% variance improved to 17% variance).

Presents 100% Confidence

Even with all your body language, chair shifting, ummming, and pre-warnings; most managers will take exactly what you say for gospel. That is because when you estimate in this fashion, you are presenting the posture to your manager, “I’m the expert and I know it will be right around 20 hours”.

Solution: Learn how to present your non-confidence in a manner that does not put the project responsibility on your shoulders. Learn to speak in estimation confidence levels that allows you to ask your manager, “I am 90% confident I can get it done in 200 hours, but if I say 100 hours I am only 30% confident. How much risk are YOU willing to take on?”


Learning to sandbag your estimates is not about tossing a couple of extra hours on a task. It is about truly understanding the things you can know, and articulating risk and concern about the things you can’t know. This way you and your manager can pad those estimations together and on the same page.



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