How to make great software estimates

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How to make great software estimates Greg Thomas

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And it begins… How long does it take to build this widget? When will you be done? Do I know what am I doing? Where do I start? What did they ask for? Did I think this through? Have I missed something? Am I as fast as Jeff?

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estimating These are all questions we ask ourselves when we, as developers, are presented with a new problem and asked to provide an estimate as to how long it will take AND when it will be ready.

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How long it will take It starts with looking at your experience, knowledge and gaining a keen understanding of the problem. It starts with 3 Core Tenants

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Experience Have I ever worked on this component? What language am I using? Do I know this language? Is this a hard problem? Do I know the platform? Do we have requirements? Is this a high-priority? When does it need to be done?

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Experience starts the process of asking yourself these questions with each problem.

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experience The person with the most practice in that particular area of development will always yield the most “near” accurate estimation as to what needs to be done and how. Experience grows over time and increases with each success and failure. You want to fail, to get better.

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Knowledge Do you know what language you are using? Do you know the underlying framework and architecture? Do you have Domain Knowledge to your field? Do you have expertise on the platform you are building on?

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What do I know that I can leverage in this estimate?

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Knowledge The culmination of everything we know applied to what we know about the problem and our experience.

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UNDERSTAND “I didn’t understand the problem” “I’m not 100% sure what to do here” “It should just work” “It didn’t do this last time” All statements that are uttered after you have started coding, but failed to take the time to understand the problem you are trying to solve.

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Never start coding if you do not understand what you are trying to code.

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Understand the problem Know the end user and identify what they expect Learn the platform/architecture that you are building on Write down your assumptions and vet them with your users, peers and team. There is no “should” when you Understand.

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When will We ship?

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Not YET We have only figured out how long it will take to accomplish our task By Understanding the Problem, leveraging our Experience and applying our Knowledge we have created an estimate that we feel can stand by. But it is not shipping time!

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SO When will it be ready?

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Your Confidence Is the most important component to any estimate. How confident are you in your estimate? 75%? 80% ? 50%? Whichever the percentage, that is your SLUSH, which is the amount of extra time you think you might need to accomplish this task.

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And what should you not apply to an estimate?

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Speed Do not build “acceleration” or “in the zone” time to your estimates. You are only as fast as you are going now. Building in future “I’m gonna know it by then” numbers will only hurt you down the road.

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No Copying NEVER use someone else’s estimates as yours. You don’t have their experience, knowledge or understanding of the problem. They are not yours, you are already behind if you take them as your own.

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No Guessing Guessing is for the lazy – “I don’t know, say 200 hours” – this means nothing, this helps with nothing, it might as well have been 2 hours as the result will have been the same.

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Good estimates Will tell you how long and when you will deliver Bad estimates Will give you nothing

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Greg Thomas