The Art and Science of Accurate Estimating


“Kris, how long will it take to implement this new design?”

“If you mean how long until we produce a product with the new design feature, I’d guess eight months.”

“You guess? Come on, we need something firm.”

“All right. I estimate it will take eight months.”

“Great. Let’s do it.”

This kind of dialogue is exchanged on thousands of projects every year. Simple as it is, it points up some of the key issues in accurate estimating. First, notice how Kris tried to clarify what was being requested before venturing a guess. Second, note that guessing wasn’t acceptable; it was only when he changed his guess to an estimate that it was taken seriously.

Estimating is forecasting the future, trying to predict the time and money necessary to produce a result. Because forecasting the future is an uncertain business, it should come as no surprise when an estimate turns out to be wrong. But a wrong estimate isn’t good enough for most project stakeholders; customers, especially, want the product on time and within the promised budget. This means that we need to focus on estimating accurately; we need to be able to predict the future in an uncertain world.

Professional estimators—those people who make their living by developing cost and schedule estimates—have developed many methods of predicting the future. When you consider how many formulas and calculations these professionals work with, it would seem reasonable to define estimating ...

Get The Fast Forward MBA in Project Management, 4th Edition now with the O’Reilly learning platform.

O’Reilly members experience live online training, plus books, videos, and digital content from nearly 200 publishers.