“Hofstadter’s Law: It always takes longer than you expect, even when you take into account Hofstadter’s Law.” — Douglas Hofstadter, American professor of cognitive science.

“Give me six hours to chop down a tree, and I will spend the first four sharpening the axe.” — Abraham Lincoln, 16th President of the United States.

Workplace productivity springs heavily from one’s skill at time management—although it’s not the only thing that determines productivity. Time management really boils down to self management. After all, how can you actually manage time itself, when we all get the same fixed amount? You can’t be so good at it that you create a 30-hour day for yourself.

Therefore, your ability to estimate a task’s duration becomes crucial when setting your schedule. Estimates come easiest when handling familiar tasks or those that include familiar elements, because experience tells you what to expect and how much time to allow for. The real issue comes when you encounter a completely unfamiliar task. How do you determine the amount of time something new will take you, without over- or undershooting significantly?

Measure Twice, Cut Once

Don’t just “guestimate” when calculating the duration of a new task. Research it by keeping the following factors in mind:

1. The Planning Fallacy. According to psychologists Daniel Kahneman and Amos Tversky, most of us underestimate how long we’ll take to complete our tasks, even when we’ve run late on similar tasks in the past. This tendency stems mostly from wishful thinking and optimism, though it often arises when our superiors push us for an estimate based on everything going perfectly. This rarely occurs, so be realistic. Don’t tell your boss it’ll take you a week to write a report because you assume you that absolutely nothing will keep you from completing 20 pages a day. Interestingly, the Planning Fallacy applies only to time estimates for one’s own tasks; we typically overestimate for other people. Therefore, you may be better off asking someone who knows you well to estimate how long they think you’ll take, then trimming the estimate somewhat.

2. Organizational guidelines. Your company may already have time estimates for a given task, based on time-and-motion studies or long-term experience, so check with to see if there are basic guidelines. For example, if you have to write a report explaining sales figures for a particular region by quarter, your company will almost certainly have formatting guidelines for reports, and may even have a stylebook for you to follow in terms of spelling, capitalization, grammatical usage, punctuation, etc. Learning a new format can add a bit of time to your estimate.

3. Your team members. Even if no one has previous documented the task, other people in your organization, your boss, or a mentor may have performed it before, or at least something very like it. So ask around. Remember, you may have to count the consultation time toward your total time estimate. If you’ll be working with other people on the task or delegating it to someone, take the abilities, deficits, and work styles of those involved into account. Some teams work together like well-oiled machines; others have their squeaky wheels. Plan for any intra-team issues you can reasonably expect.

The Eternal Enemy

If you still can’t pin down how long something will take, better to overestimate than underestimate. Be a little pessimistic, deliberately building some flexibility into your schedule. If you finish early, you’ll have extra time to apply toward something else.

We all face scheduling conundrums occasionally. If experience doesn’t offer any guidelines for an unfamiliar task, use the tips I’ve outlined here to narrow the field. If they don’t help, then make your best guess. You may be dreadfully wrong; but even so, the next time you encounter that task, you’ll have a better basis for your estimate.