Mind Performance Hacks

Hack #41. Estimate Orders of Magnitude

By using rough order-of-magnitude estimates, you can check calculations and estimate whether tasks are even plausible before spending time to plan them more accurately.

An order-of-magnitude estimate is an estimate to the nearest power of 10. For instance, an order-of-magnitude estimate of 400 means the true value is closer to 400 than 40 or 4,000. The estimates we're discussing in this hack are called rough order-of-magnitude (ROM) estimates because we're not completely sure we're within an order of magnitude.

Other terms for this kind of estimate are ballpark estimates (as in, "Are we even in the ballpark?") and educated or scientific wild-ass guesses. As all of these names suggest, the idea is to determine roughly how large a number is, or whether a task is trivial, possible, or absurd.

Warning

When you're estimating tasks, make sure everyone understands that ROM estimates are just that. They should not be written into contracts or used as targets when actually doing work. That needs more careful estimation and project tracking. ROM estimates are just to know whether to bother performing a more formal estimate.

In Action

First, let's do a purely numeric hack: estimate how many seconds are in a year.

There are 60 seconds in a minute and 60 minutes in an hour; multiplying them is easy: 3,600 seconds in an hour. Let's round that to 4,000. Twenty-five percent might seem like a big round-up, but we are concerned here with orders of magnitude; as ...