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Estimating Time For Project Tasks: How To Do It (+Examples)

In my previous article, I talked about some of the time estimation techniques for projects. In this article, I want to talk about how to estimate time for project tasks. Follow me as we will look at that together in this article.



Accurate activity time estimates form the basis of an accurate project schedule because it includes a careful review of the effort required, the duration of tasks, the delivery date or deadline, and customer priorities.


To ensure that your estimates are as accurate and realistic as possible, follow these guidelines:

#1 Gather documents

There is a need for you to gather all prerequisites, such as activity lists, activity attributes, resource calendars, activity resource requirements documents, and project products required to estimate the duration of each activity in the project.


#2 Involve work package owners

There is a need for you to involve work package owners or others who are familiar with the work or activity.


In general, the people responsible for doing the work are the ones who can best estimate the effort and duration for the activities under their control.


The project manager will, however, be responsible for actually making the estimates, based on the number provided by experts.




In some cases, the project manager may take the sole responsibility for making the duration estimates.

Some examples are:

  • Small projects in which the project manager is familiar with the activities required.
  • Projects with activities that are well defined and for which there is good historical information from similar past projects.


#3 Consult historical information

You need to consult historical information about past projects and ask the following questions :

  • Are there any detailed records from previous, similar projects that you could use to derive your estimates?
  • Are there any relevant commercial duration estimates techniques?
  • Do any project team members have experience with similar activities.?

#4 Appropriate technique

You have to determine which appropriate technique you want to use to estimate the activity duration.


The techniques include analogous estimating, parametric estimating, three-point estimating, as well as reserve analysis.



#5 Work quantification

You have to determine how you want to quantify the work that needs to be done in terms of the estimates hours of labour that will be needed, the number of units to be produced and the number of customers to be served.

#7 Consider resource requirements

There is a need for you to consider the resource requirements and capabilities of available resources within and outside the organisation. You need to ask:

  • Which people will be assigned to this activity?
  • How will the skills of the assigned staff affect duration estimates? You know it will take a longer time for an inexperienced person to finish a task than someone that has the required experience.


#8: Appropriate Estimation method

You need to determine the appropriate estimation method to use for the project. You need to ask the following questions :

  • If it is early in the planning phase or if there is good historical data, consider using an analogous estimating technique.
  • If there is inadequate historical data, consult Subject Matter Experts.
  • Use quantitatively based duration to estimate activities when quantities of the work unit can be multiplied by the productivity rate.
  • If you are using the Three-point estimating technique, ask the estimators for the best-case, most likely and worst-case estimates.


#9 Consider constraints

When it comes to estimating time for your project, you need to look at the assumptions and constraints for your project.


What are some of the impediments that you have discovered that are likely to come up during project execution?


You have to confirm whether the assumptions and constraints are still real before you continue with your project.



#10 Verify the accuracy

There is a need for you to also verify the accuracy of your estimates when you estimate the duration for your project. You need to ask the following questions:

  • What is the probability associated with the estimate?
  • What was this estimate based upon?
  • Is there any risk associated with this estimate?


#11 Consider the reserved time

In order not to have an abandoned project, there is a need to have a second look at your reserved time. Have you created enough time for delays that come up.


You have to make sure that the extra time is being calculated based on the capacity of your resource.


#12 List of assumptions

It is not every time that you have “all greens” before your project can start. There are times that you just have to assume and start the project.


In calculating the duration of your project, you have to factor in assumptions and constraints that you have discovered before you begin the project. Some might come to pass and some might not.



13 Range of variance

It is not always possible for your coat and time estimate to be one hundred percent accurate. If that is the case, you need to discover the range of variance between your normal estimate and what is likely to happen on your project.


This will allow you to factor that into your time calculations.



#14 Update documents

Most times, after changes have been made to your document and you have discovered the actual time that it will take to execute your project, you need to make sure that all documents are updated.


You have to note that whatever affects the time will definitely affect the coat and scope of your project.



Typical example…

The project manager for the company’s website project, Paul, asked his work package owners to provide estimates for each of their activities.



The art director, Tracy, needs to hire a contractor to do the design work. Also, she is unsure of how long the design reviews will take. Based on these factors, she submitted an activity estimate to Paul.



Tracy estimate defines work as days according to Paul specifications.



Her estimate specifies who will be used on the project and how their skills will affect the duration. She has used a quantitative method for her estimate and included relevant assumptions made earlier.



Finally, Tracy’s estimate includes a range of variance for each duration.

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