Something to doWorkload & wellbeing
Add a buffer to your estimates
A simple exercise to give dates from what actually happened last time, not from your best week
Why it’s worth your time
Estimates tend to describe the best week, not the likely one. When you picture a task, you picture it going smoothly, and the interruptions, the waiting and the surprises don't show up. Checking how long similar work really took gives you an honest starting point, and a buffer you can explain covers the rest.
How to estimate how long work will take
You’ll come away with a date based on what actually happened last time, with room you can explain.
We’ll turn this into a checklist you can tick off.
- Make your gut estimate.
Go with the number that comes to mind. You'll check it in a moment, so don't agonize over it.
- Find the last similar job.
Something close in size or shape. Check your calendar, your sent messages or the ticket history for when it started and when it actually finished.
Tip: Count calendar days, not hours of effort. The waiting is part of how long it takes.
- Compare, and start from what happened.
If the last one took twice what your gut would have said, your gut is probably running optimistic this time too. Let the real number lead.
- Add room for what's new.
Anything you haven't done before, anyone you're depending on, anything that needs an approval. Each is a place to add a little time.
- Give the date, with the reason if it helps.
Then note the date you gave. When the work is done, jot the real finish next to it. After a few of those, your gut gets better.
You“Realistically, next Wednesday. The last report like this took about a week once reviews were in, so I'd rather give you a date I'll hit.”
Good moments for this: every time you give a datefor anything longer than a few dayswhen you're new to a kind of work
We’ll turn this into a checklist you can tick off.
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Making it work for you
Every workplace is different. Here’s what to think about before you start, and what might get in the way.
Things to think about
It isn't a personal failing. People tend to imagine the version of a task where nothing goes wrong, even when they remember that last time plenty did.
What might make this harder
Give both: what's possible if everything goes right, and what you'd commit to. Let them choose which to plan around, knowing the difference.
Questions people ask
How do I estimate how long a task will take?
Start from how long something similar actually took, counting the waiting, then add room for anything new or dependent on other people.
What is the planning fallacy?
The tendency to underestimate how long your own tasks will take, even when similar tasks ran late before.
How much buffer should I add to an estimate?
There's no single right amount. Your own history is the best guide: if similar work usually runs over by a certain share, start there.
Is it okay to pad estimates at work?
Hidden padding can erode trust. A buffer you can explain, based on how long similar work took, tends to read as honest planning.
Why this works, and where it comes from
If you've ever been sure something would take two days and watched it take six, you're in good company. When we imagine a task, we imagine it going well. The meeting that runs long, the reply that takes three days, the part that turns out harder than it looked don't appear in the picture, because they haven't happened yet. So estimates come out describing our best week, and we live in ordinary ones.
The psychologists Daniel Kahneman and Amos Tversky named this the planning fallacy. The striking part is that experience doesn't cure it: people underestimate their own tasks even when they clearly remember that similar ones ran late. The correction Kahneman later argued for is taking the outside view, looking at how long cases like this one actually took, instead of reasoning from the inside about how this one should go.
That's what this exercise is, made small enough to do before you answer. Truest's version adds one habit: write down the date you gave and the date the work actually finished. After a few of those, you have your own history, and your gut starts to learn from it. A buffer grounded in what really happened is also easy to explain, which is the difference between planning and padding.
The point is never to give slow dates to protect yourself. The people waiting on you need a date they can build on, and a realistic one serves them far better than an optimistic one that moves. If someone needs it sooner, that's a real conversation about what to cut, and it's much easier to have before you've promised than after.
Other simple things to consider
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Written by Truest, based on Intuitive Prediction: Biases and Corrective Procedures (Daniel Kahneman and Amos Tversky), Timid Choices and Bold Forecasts: A Cognitive Perspective on Risk Taking (Daniel Kahneman and Dan Lovallo) and Exploring the "Planning Fallacy": Why People Underestimate Their Task Completion Times (Roger Buehler, Dale Griffin and Michael Ross). Last updated September 25, 2026. We sell a career membership; where that’s relevant above, we say so.