Apply your documented error factor to timeline estimates…
After identifying that you are systematically overconfident on timelines by X%, multiply your initial timeline estimates by (1 + X/100) before stating them publicly.
When This Fires
- Estimating project timelines, sprint commitments, or delivery dates
- Providing time estimates to clients, managers, or stakeholders
- Planning your own work schedule or setting deadlines
- Any domain where you've documented that your estimates are systematically off
Common Failure Mode
Believing "this time is different." Every new estimate feels like it accounts for the lessons of the last one. But the planning fallacy operates below conscious correction — your intuitive estimate is generated by the same biased process regardless of how many times you've been burned. The correction factor works precisely because it's mechanical: it doesn't trust your intuition, it adjusts it.
The Protocol
(1) Make your intuitive estimate as you normally would. (2) Check your documented error factor for this domain (you need a track record of at least 10 past estimates vs. actuals). (3) Apply the formula: multiply your estimate by (1 + X/100). (4) State the corrected number publicly. It will feel too generous — that feeling is the planning fallacy in action.