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Outside view timeline estimator
Paste your project and your estimate. Get the estimate corrected by how projects like it really went.
Outside view timeline estimator is a free AI prompt for the job "Think it through and decide". Give the instructions to an AI assistant that supports the required files and tools, then review its output.
Free · No account · Made by AI Blocks · Level: beginner
What it does
Every project estimate is made from the inside: this task, these people, this plan, and it feels like six weeks. Daniel Kahneman has described in public why that view is almost always too hopeful, and the fix: ask how long projects like this one took, and start from that number instead. This prompt takes your estimate and the plan's reasoning, names the class of project it belongs to, and builds the record from your own history, with the ratio of actual to estimate for each past project and the median. It multiplies your estimate by that ratio and shows the range. It then tests each reason you think this time is different, accepting only the ones that truly change the class, marks the steps that usually run long, and gives you the number to promise with the sentence to say. With no history, it says so and labels its ratio…
You give it
- The project and your estimate, with the plan's reasoning
- Past projects of the same kind, with estimate and actual (advised)
- Why this time is different (optional)
- Your lessons (optional)
You get
- The reference class and your record with the median overrun
- The outside estimate with its range, arithmetic shown
- Each 'different this time' reason rated
- The steps to watch and the number to promise
Use it when
- You are about to promise a launch date to a customer, a board or your team.
- Your last three projects all ran late and this estimate looks like the last three.
- Someone says 'this time is different' and you want to check.
How to use it
- Copy the prompt, then paste it into Claude, ChatGPT or Gemini with your plan and estimate under it.
- Dig out three to five past projects with their estimates and actuals.
- Read THIS TIME IS DIFFERENT. Argue only with the ACCEPT lines.
- Promise the PROMISE number, not the inside one.