We have all been there.
It’s Tuesday. A client asks for a quote on a “simple” project. You look at the brief. It looks standard. You think, “I can smash this out in two days.”
You quote for two days. You promise delivery by Thursday.
Fast forward to Thursday evening. You are stressed, half-finished and eating toast over your keyboard while the client emails asking for an update.
What happened? You didn’t get lazy. You didn’t lose your skills. You fell victim to The Planning Fallacy.
What is the Planning Fallacy?
The Planning Fallacy is a cognitive bias first described by Nobel Prize winner Daniel Kahneman. It states that human beings display an optimism bias when predicting their own tasks.
We assume the best-case scenario. We imagine a world where the software doesn’t crash, the research is easy to find, the client doesn’t ask for a “quick tweak,” and we don’t get a headache.
But as freelancers, we don’t work in a best-case world. We work in the real world.
If you base your quotes and deadlines on your “happy path” estimate, you are setting yourself up to work evenings and weekends for free just to catch up.
The Solution: The Navy’s Secret Weapon (PERT)
To fix this, we need to stop guessing and start calculating.
In the 1950s, the US Navy developed a technique to manage massive, complex projects (like building nuclear submarines). It’s called PERT (Program Evaluation and Review Technique).
It sounds complicated, but for a freelancer, it is surprisingly simple. Instead of giving one estimate (e.g., “3 days”), you give three:
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The Optimistic Estimate (O): Everything goes perfectly. You are in the flow state. The API connects first time.
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The Most Likely Estimate (M): A normal day. A few emails interrupt you, but you get it done.
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The Pessimistic Estimate (P): Everything goes wrong. Your laptop updates Windows for 2 hours. The client sends the wrong files. The Wi-Fi drops.
The Formula
Once you have these three numbers, you don’t just average them. You use a weighted average that leans heavily on reality, but respects the risks.
This formula gives you a Safety-Adjusted Estimate. It forces you to acknowledge the Pessimistic scenario, pulling your final number away from the delusion of the Optimistic one.
Try It Yourself
Stop guessing. Use the calculator below to generate a deadline you can actually stick to.
How to Use This Number
Let’s say your “Most Likely” guess was 3 days. But the calculator gives you a result of 4.2 days.You have two options:
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The Quote: Quote the client for 4.5 days. This ensures you are paid for the risk you are taking.
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The Deadline: If you charge a fixed fee, stick to your original price if you must, but tell the client the work will be delivered in 5 days.
This buys you a “Buffer.” If everything goes wrong (the Pessimistic scenario), you are covered. If everything goes right (the Optimistic scenario), you deliver the work early.
Result: You look like a hero for delivering early, rather than an amateur for delivering late.
