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Resources Work out your leave-by time

Work out your leave-by time

Log a few real times to find your own multiplier, then work backwards from when you need to arrive.

The short version

  • Enter two or three tasks with what you predicted and what they actually took. The tool works out your personal multiplier (the amount your predictions tend to run short by) instead of asking you to predict better.
  • Then name where you need to be and when, and list the hidden parts nobody counts: finding keys, the walk to the stop, the queue. The tool applies your multiplier and works backwards to a realistic leave-by time.
  • This returns nothing about you. It rearranges the numbers you type and hands them back in a sentence you can act on.

People underestimate how long their own tasks will take, and they do it even when they know they have underestimated the same kind of task before. Knowing about the effect does not remove it. So this tool does not try to fix your sense of time, it puts the time outside your head, measures how far your predictions run short, and works backwards from the arrival rather than forwards from the departure.


Before you begin

Have in mind two or three recent tasks where you can honestly say both how long you thought they would take and how long they really took. Then have in mind one upcoming thing you need to arrive at on time. Nothing you type is saved.

Worth knowing. People underestimate how long their own tasks will take, and they do it even when they know they have underestimated the same kind of task before (Buehler, Griffin & Ross, Journal of Personality and Social Psychology, 1994). The planning fallacy is well established and has been replicated across many task types. It is a general finding about people, not about any particular group. Working backwards from an arrival time, and applying a measured multiplier rather than trying to feel time more accurately, is a response to that finding rather than a claim of its own.

Nothing here is saved or sent anywhere. What you type exists only while this page is open.

Written for Thought Club as general guidance, not medical advice. Free to read, print, and share.