Estimating how long a development task will take is notoriously difficult. We’ve all encountered tasks initially estimated to take a few days, only to see them stretch over several weeks.

Contrary to what you would expect, an estimate doesn’t always become better if you put more effort into it. An estimate given as a rough guess during a brief discussion with your PM might be more accurate than one derived from a lengthy refinement session with your team. That’s because when you break it down into small tasks you tend to miss the unknowns. Of course, having a refinement session and breaking tasks down into smaller parts is usually very beneficial to do anyway. But you should not expect a more precise estimate by doing it.

Be wary of giving an estimate to meet someone else’s expectations. The point of the estimate is to get an idea of how long something will take. The point is not to make a stakeholder happy. If a manager or PM has a habit of questioning estimates, then they are skewing them.

Avoid thinking about how long time something will take. This sounds like a contradiction, since estimations are exactly about guessing how long time something will take. But it’s usually easier to compare different tasks to each other. I.e. saying that task A is about the same size as task B is easier than saying that task A will take 7 days to complete. When you think something will take 7 days then usually you will think about 7 uninterrupted days. But you rarely have a day with no interruptions, much less 7 days.

Lastly, it’s worth questioning why you need an estimate at all. Knowing if something will take 3 weeks or 6 months is useful. That’s a question a PM would ask early on when determining what tasks to prioritize for the next quarter. But is it really useful to know if something will take 1 day or 3? When tasks are small enough to be assigned to a single person to work on, it might be simpler to just count tickets and not differentiate the sizes between them. For example, you might say that in 2 weeks we can complete 7 tickets, and not care what the individual sizes of those 7 tickets are.