Planning fallacy explained
We plan from the inside, imagining the task going smoothly, instead of looking at how long similar work really took. Interruptions, unknowns and rework do not appear in that picture.
Using an outside view, the actual track record of similar projects, gives far more realistic estimates.
Try it today
- Find two or three similar past tasks and how long they took.
- Base your estimate on that, not on the best case.
- Break the task into steps; small estimates are more accurate.
Where it comes from
Psychologists Daniel Kahneman and Amos Tversky proposed the term in 1979. Later work by Lovallo and Kahneman (2003) widened it to costs and risks.
Frequently asked questions
- What is the planning fallacy?
- The planning fallacy is the tendency to underestimate how long a task will take, even when you know similar tasks have run late before.
- Where does the planning fallacy come from?
- Psychologists Daniel Kahneman and Amos Tversky proposed the term in 1979. Later work by Lovallo and Kahneman (2003) widened it to costs and risks.
- How do I start with the planning fallacy?
- Find two or three similar past tasks and how long they took. Base your estimate on that, not on the best case. Break the task into steps; small estimates are more accurate.
- Which tools help with the planning fallacy?
- Tools in our directory that help include Toggl Track, Linear, Motion, Rize. Each has its own page with pricing, pros and cons.