We are surprisingly bad at predicting how long things will take. Even with plenty of experience to draw on, a quick email can become half an hour and a simple errand can absorb an afternoon. We often plan according to how long we think something should take rather than how long it has actually taken before.
Psychologists have studied this tendency for decades. Understanding why it happens can help you find practical ways to make more realistic estimates.
Why It Happens: The Planning Fallacy
Researchers Roger Buehler, Dale Griffin, and Michael Ross explored the planning fallacy in a series of studies published in 1994. Participants consistently made optimistic predictions about when they would finish academic and everyday tasks. Their estimates followed the plan they had in mind more closely than the time similar tasks had taken in the past. When participants were prompted to consider relevant past experiences, their estimates became more accurate.
This tendency toward optimistic planning can cause problems because we imagine tasks as a straightforward sequence. Writing a report means opening the document, writing, editing, and sending it. The estimate can leave out the time spent looking for information, answering a message, changing direction, or figuring out a problem.
Looking at previous experience provides another source of information. If the last three reports took between 90 minutes and two hours, that gives you a more useful starting point than an optimistic 45-minute estimate.
The Planning Fallacy and Neurodivergence
Underestimating time is a common human tendency. Some neurodivergent individuals may also experience differences in time perception and executive function, which can make planning and estimating time more difficult.
Time perception is our ability to judge the passage of time and estimate how long an activity has lasted or will take. Research on ADHD has found differences in several aspects of time perception, including the estimation and reproduction of durations.
Executive function refers to a group of cognitive skills that help us plan, organize, manage attention, hold information in mind, and shift between tasks. Research has identified differences in several executive function domains among people with ADHD, including working memory and planning.
When it comes to everyday situations, both time perception and executive function can come into play. “Get ready to leave” seems simple, but it may involve finishing what you’re doing, gathering your things, getting dressed, using the bathroom, finding your keys, and making the transition out the door. Each step takes time, and each transition requires some mental effort.
Making More Realistic Time Estimates
1. Pay Attention to Energy
The amount of time available isn’t the only factor that affects how long a task takes. Energy, concentration, interruptions, and the difficulty of the task itself can all change the pace of a day.
Notice when demanding work tends to come most easily and when concentration becomes harder. Build breaks and transition time into your schedule. When estimating a task, think about your usual working conditions. An unusually productive day or a period of intense focus can make a task seem faster than it typically is, so it may not provide a useful basis for planning.
2. Make Time Visible
A visual timer gives the passage of time a physical, immediate presence. With Time Timer, the colored disk gradually disappears as the minutes pass, making the remaining time easy to see.
Before you begin a task, estimate how long the task will take. Set the Time Timer and watch how the time actually unfolds. When you’re finished, compare your estimate with the time the task took.
You can also use a visual timer to break a larger task into manageable periods. Set a 20-minute timer for a task, for example, and see what you can accomplish within that window. Over time, these observations can help you develop a more accurate sense of how long similar activities take.
3. Build In Buffers
Most estimates leave little room for getting started, switching between activities, finding something you need, or dealing with an interruption. Build some of that time into your schedule.
The buffer time you need will depend on the task and your own routines. If you know that getting out the door usually involves a few unexpected delays, account for them when you plan. A time audit can help you identify where those extra minutes tend to go.
4. Do a Time Audit
Choose a few activities you regularly underestimate and record how long they actually take over the course of a week. Getting ready, answering emails, cooking dinner, and driving to a standing appointment might be good places to start.
You don’t need to track every minute of your day. A handful of recurring tasks can give you useful information about how long things actually take and help you build that knowledge into future plans.
5. Break Tasks Down
Some tasks contain far more steps than their name suggests. “Do the laundry” sounds like one task, but it involves gathering clothes, sorting them, loading the washer, moving the clothes to the dryer, folding them, and putting them away. Work projects often contain the same hidden steps. Preparing
Breaking a task into its component parts makes those steps easier to see and gives you a better basis for estimating how long the whole task will take.
Build a Better Estimate
Over time, paying attention to your energy, tracking how long tasks take, and building that information into your schedule can make your estimates more realistic
The next time you catch yourself thinking, “That should only take 20 minutes,” take a closer look at what the task involves. Think about when you last did something similar, how long it took, and what might need to happen along the way. The more information you have about your own routines, the more useful your estimates become.
