roject managers aren’t fortune-tellers. Yet that’s
exactly what the job calls for: knowing in advance
what a project will cost, how long it will take and
what resources it will need.
When project practitioners’ initial estimates
don’t match up with reality—when the project goes
over budget and beyond schedule—it doesn’t always
mean the project failed during execution. It could
mean the initial cost and timeline estimates were
faulty in the first place.
“It is crucial to create reasonable estimates
and set manageable expectations,” says Gaurav
Chauhan, PMP, senior manager of projects for
international property consultancy Knight Frank,
Still, Mr. Chauhan says, estimating errors happen all too frequently. The consequences are clear:
A megaproject to extend a commuter rail line in
New York, USA—the largest ongoing transportation infrastructure project in the country—has gone
more than US$6.5 billion over budget and 14 years
beyond schedule. The culprit, according to a former
project lead, was an unrealistic initial estimate.
Here are eight common causes of estimating
errors, as well as the best ways to avoid them.
—Gaurav Chauhan, PMP, Knight Frank,