Tips to estimate the required time for a task precisely

In the last article "Can you give an immediate answer about when you can finish an assigned task?", I described that you can answer the accurate delivery date if you can only estimate the required time for each task. However, it should be difficult to estimate the required time in practice. So I think about the way of improving the accuracy of estimating the required time in this post.


Why did I fail to meet the deadline?

In fact people who are not good at estimating the required time have something in common. It is that the volume of a task is too big. Let's talk about the real story. It was the story when I was new to a company. I was offered making some documents and talked with my boss like this:

Boss : "How long does it take to complete the work?"
Me : "One week is enough."
Boss : "You have to solve some problems to make these documents. Are you OK?"
Me : "I'm guessing all right."
Boss : "How many hours do you consider the volume of all tasks as?"
Me : "About 5 hours."
Boss : "Why do you think so?"
Me : "Ummm, based on my past experience..."

My plan in this time was about as follows:
"2 days for considering, 3days for making documents, and the total required time is 5 hours."
It was too rough and to tell the truth, time is a guess. The result was as you would guess. Eventually the total required time was 9 hours and it took 2 weeks to complete all the tasks. I mean, my estimation was wrong.

While there were some causes of my mistake, the biggest problem was that I estimated the required time without the image of each task. Why couldn't I imagine the content of each task? That was because each task was too big.


Break a big task into small pieces

When you work on a big and complicated task, you need to break the task into small pieces. As for making documents described above, I could estimate the required time more accurately if I broke the task into small pieces like this.

[Consider issues]
Consider the issue 1 : 30 min
Consider the issue 2
  Interview people involved : 30 min
  Consider the solution : 60 min
Consider the issue 3 : 40 min

[Make documents]
Survey documents : 90 min
Consider the structure of documents(deliverables) : 30 min
Make key messages : 60 min
Wite the chapter 1 (tentative) : 30 min
Wite the chapter 2 (tentative) : 90 min
Wite the chapter 3 (tentative) : 60 min
Arrange documents : 20 min

Breaking a big task into small pieces makes what you should do clear and I think you can estimate the required time accurately. By the way, "tentative" means that you get to know the volume of the task after finishing "Consider the structure of documents(deliverables)". In this way, by breaking a big task into small pieces, you get to know unconfirmed elements and be able to hedge the risk e.g. telling your boss the possibility of changing the plan.


Tips to estimate the required time for a task precisely

It is "the required time for one task is less than 90 min." that I want you to be conscious of to estimate the required time. It is said that an attention span of a grown-up is 90 min at most, for example, the length of a class at a university is often for 90 min. While I think an attention span differs according to people or conditions slightly, I recommend that you consider the upper limit of the required time for a task as 90 min.


The summary

In this article, I described that the key point to estimate the required time accurately is breaking the task into pieces. And this is the same as task design I described in "Paper planners are tools for people who are good at task management.". While I think you worry about an appropriate size of a task when you design tasks, the answer is that you have to break a big task into pieces to the level that the following two conditions are met.

  1. The content of each task is concrete enough to estimate the required time.
  2. The required time is less than 90 min.