Why Do I Always Think I'll Have More Time Next Week?
Why do I think I'll have more time next week? The planning fallacy, the measured gap between predicted and actual time, and what closes it.
Gizella Nagyne Palinkas
10/29/20267 min read
The short answer
Because when you picture next week, you picture the plan — not the interruptions, the tiredness, or the three other things that will also be true that week. Psychologists call this the planning fallacy, and it is one of the most reliably measured biases there is: in one study of students finishing their senior theses, the average prediction was 33.9 days and the average reality was 21.7 days longer than that. Knowing about it does not fix it. One specific change in how you make the estimate does, and it is at the bottom of this page.
What is happening psychologically
When you ask yourself "how long will this take?", your mind does something quite specific: it builds a little film of the task going well. You sit down, you start, it flows, you finish. That film is detailed, vivid and entirely about this task.
What the film leaves out is everything that is not the task: the email that arrives, the afternoon you cannot concentrate, the part you had forgotten about because you had not started — and your own history of this exact thing taking longer than you thought.
That is the oddity at the centre of the planning fallacy. People are not generally optimistic about how long things take. They are optimistic about this one, while cheerfully agreeing that everything else always overruns.
"Next week" is the ideal container for that film, because next week is still empty. It has no interruptions in it yet. By the time it arrives it will be as full as this week, but from here it looks like open ground.
What the research says
The planning fallacy has been measured many times, and the numbers are remarkably consistent. The figures below are all reported in an NBER working paper on the planning fallacy, which surveys the experimental literature.
Buehler, Griffin & Ross (1994), Study 1 — students finishing a senior thesis. "The mean predicted time to completion is 33.9 days, 21.7 days shorter than the mean actual completion time." So the average prediction was about 34 days and the average reality about 56.
Buehler, Griffin & Ross (1994), Study 2 — ordinary academic and non-academic tasks. Average predicted versus actual times were 5.8 versus 10.7 days for academic tasks, and 5.0 versus 9.2 days for everything else. Both roughly doubled.
The confidence number is the one that stings. In that same study, "only 37 (43) percent of subjects completed their academic (non-academic) tasks in the time they predicted" — while they had been "74 (70) percent confident they would." Three quarters felt sure. About four in ten made it.
It is not that predictions are random. The correlation between predicted and actual times was 0.77 in the thesis study: people knew which tasks were the long ones, and were simply wrong in the same direction about all of them. That is what makes it a bias rather than noise. It replicates, too — across eight studies reviewed by Roy, Christenfeld & McKenzie (2005), "the mean prediction is 4.7 days or 26 percent less than the mean actual completion time."
Study 4 is the one that contains a fix. When participants were steered to recall relevant past experiences before estimating — specific memories of similar tasks, not "think harder" — "the mean predicted and actual times to completion were the same (both 7.0 days)." The gap closed completely.
An everyday example
A form has been on the fridge for three weeks. Every Sunday you move it to "next weekend", because it needs a proper free morning and this weekend does not have one.
Look at what is happening in that sentence. You have estimated that the form needs a morning. You have never actually sat down with it, so that estimate came from the feeling of dread attached to it rather than from the form. The real work is probably forty minutes.
Meanwhile "a free morning" is being promised by a future week that is currently empty and will not stay that way. So the task is waiting for a resource that does not exist, on the strength of a size estimate nobody has checked.
That is the planning fallacy in its most ordinary clothes: not a missed deadline on a big project, but a small job that quietly does not happen for a month.
What this does not necessarily mean
It does not mean you are lazy, disorganised, or bad at planning. The students in those studies were not — their predictions correlated strongly with reality; they were simply shifted.
It does not mean you have a problem with procrastination. Procrastination is avoidance of starting. This is a mis-measurement of size, and the two often look identical from outside while needing completely different fixes.
It does not mean something is wrong with you in a clinical sense. This is a pattern, not a verdict on anybody — including yourself, and including whoever in your house keeps saying they will get to it next week.
And it does not mean "just be pessimistic". Padding every estimate by an arbitrary multiplier mostly produces estimates you do not believe, which you then ignore.
Practical things to try
1. Estimate from memory, not from imagination. Before you guess at a number, ask: when did I last do something like this, and how long did it actually take? This is the move that closed the gap to zero in Study 4. If you have never done it, ask someone who has.
2. Break it into the parts you would actually do. "Sort out the paperwork" has no size. "Find the letter, fill in two pages, scan it, email it" has four sizes, and adding them up produces a number much closer to reality than estimating the whole.
3. Put the first slice in an ordinary day. Not the whole task in a free day — the first twenty minutes in a normal Tuesday. Stop when the time is up. Most tasks saved for a free morning turn out to be forty-minute tasks wearing a costume.
4. Keep one week of actuals. For seven days, write the estimate before you start and the real time after. Two columns. After a week you have your own multiplier, which beats any published average.
5. Stop using "next week" as a container. It is only empty because it has not happened yet. If something needs a block of time, put it in the calendar at a named hour, this week.
6. Notice the relief. A flash of relief when a free day gets cancelled is a signal: the task was never going to happen that day either, and you knew it.
When professional help may be appropriate
Almost nobody needs help with the planning fallacy — it is an ordinary feature of how estimation works, and the tools above are the whole of it.
It is worth talking to a doctor or a psychologist if something more than time estimation is going on: if tasks go undone to the point where work, money, health or relationships are affected; if the avoidance comes with persistent low mood, anxiety or exhaustion; or if difficulty starting things has been lifelong and shows up everywhere rather than on one dreaded form. Mind Decoded describes patterns in everyday behaviour and does not diagnose anyone.
Try the quiz: how big is your estimating gap?
Six questions, two minutes, and it sorts your relationship with "next week" into one of four patterns — each with three or four specific things to try.
Frequently asked questions
Q: What is the planning fallacy, in plain English? A: It is the well-measured tendency to underestimate how long your own task will take, even when you know perfectly well that similar tasks have overrun before. The reason is that when you estimate, you picture the task going smoothly and in isolation — the detailed film in your head contains the work but not the interruptions. It was named by Daniel Kahneman and Amos Tversky, and it has been reproduced across dozens of studies since.
Q: Why do I think I'll have more time next week specifically? A: Because next week has not been filled in yet. This week's interruptions are visible and next week's are not, so a future week looks like open ground in a way the current one never does. By the time it arrives it will contain roughly the same amount of life as this one. The fix is to stop treating "next week" as a resource and put the work in the calendar at a named hour instead.
Q: Does knowing about the planning fallacy stop it happening? A: Mostly no, which is one of the more irritating findings in the area. Awareness alone does not shift estimates much, because the bias lives in how the estimate is generated rather than in what you believe about estimates. What does work is changing the generating process — recalling what a similar task actually took, or breaking the task into the specific steps you will perform, so the number is built from parts rather than from a feeling.
Q: Is the planning fallacy the same as procrastination? A: No, though they produce similar-looking weeks. Procrastination is avoiding starting something, often because of how it makes you feel. The planning fallacy is getting the size wrong — you fully intend to do it, you have simply budgeted a third of the time it needs. They need different responses: the first is about lowering the cost of starting, the second is about correcting the estimate. Many stalled tasks have a bit of both.
Q: Why am I confident even though I am usually wrong? A: Because confidence is generated by the same vivid film as the estimate. In Buehler, Griffin and Ross's study, students were around 74 percent confident they would finish academic tasks in the time they predicted, and only about 37 percent did. The feeling of certainty tracks how clearly you can picture the task, not how often you have been right before. Padding estimates by a fixed multiplier helps a little, but a week of your own recorded actual times helps more.
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The Procrastination Daily Planner is a five-page printable built around exactly these moves: one thing and a tiny first step, an if-then plan, a task breakdown, and a worksheet for the question "why am I avoiding this?" Undated, A4 and US Letter, instant PDF.
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It is a self-reflection tool, not therapy or medical advice, and it does not treat or cure anything.
Sources
National Bureau of Economic Research Working Paper 14228, "An Economic Model of the Planning Fallacy" — https://www.nber.org/system/files/working_papers/w14228/w14228.pdf — the source of every figure quoted above. It reports the empirical results of Buehler, Griffin & Ross (1994), Journal of Personality and Social Psychology 67(3), 366–381, and the review by Roy, Christenfeld & McKenzie (2005).
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