Estimating Activity Duration for Your Project Plan and Schedule


“How long do you expect this to take?” asked the project manager to the lead developer who was in the throes of figuring out a complicated algorithm for her latest project. “About 40 hours,” she said somewhat dismissively.

“40 hours? Really? You think it will take that long? It’s really not that involved,” the PM countered.

“Yep. 40 hours,” she said. “Can I get back to work now?”

How many times have you had that conversation? What’s especially frustrating is that every deliverable you ask this particular developer about is going to take 40 hours! It’s her standard and pat answer to everything. It’s her way of getting you off her back so she can get back to her current work.

You understand that she’s busy, but you really need this information to update the project plan and schedule.

Estimating how long a particular deliverable will take is a challenge for all project managers. There are so many variables, what-ifs, and contingencies to estimating activity duration that arriving at an accurate project plan and schedule can seem to be next to impossible.

What Makes Estimating Activity Duration So Complicated?

You will find that you are dealing with three different numbers when you are estimating durations for a project plan and schedule. These are:

  1. How Long Someone Says Something Will Take: The first numberHow long someone says something will take is nothing more than a crystal ball estimate you will come across when you are putting your project plan and schedule together is how long someone thinks something will take.This is when you go to the developer, tester, DBA, designer, technical writer, or other resource and ask for their input. You describe to them what needs to be done.

    They will then come back to you with an estimate of how long they will need to complete the task. This is based upon their expert opinion, similar deliverables, and educated guesswork.

    Most resources are pretty good at getting you in the ballpark. However, the ballpark is a big place. Newer resources will have a tendency to underestimate how long something will take to complete.

    More experienced resources will have a tendency to overestimate how long something will take to complete.  They have learned to factor in the start/stop nature of interruption driven and meeting-laden work cultures.

  2. How Long you Want Something to Take: The second number you will need to work with when you are putting a project plan and schedule together is how long you want (or need) something to take.There may be some constraints in place that you must be mindful of as a project manager. Commitments may have been made to a customer, or there may be a Board meeting coming up where the next greatest thing is going to be demoed.

    This number is typically going to be a bit more aggressive than the number provided above. Thus, the ongoing dialogue that occurred at the beginning of the article.

  3. How Long Something Actually Takes: This number is knownHow long something actually takes is known as 'reality' as ‘reality’. It will most likely come in close to what the team resource originally quoted. Sometimes, this number may blow past what the original estimate was by 2 or 3 times!This is important information to know for future purposes of putting your project plan and schedule together. There is nothing more accurate than understanding the actual time that something took to complete. This should be used as the starting point for future project estimates.

    Understanding how long something actually takes means that you have a system in place for accurately capturing time and attributing this time toward a particular deliverable. The system doesn’t need to be overwhelmingly complicated.

    Your team does need to use the time tracking system you have in place consistently and accurately. This will allow you to base future estimates for your project plan and schedule on reality.

Understanding that there are three different numbers you will be working with during project planning can make the process a bit simpler. It can help you arrive at a range of durations that fall into best case, likely case, and worst case.

Watch Out for These Project Plan and Schedule Traps!

There are a number of traps that you may encounter during the planning process. Watch out for:

  • You Really Like the Low Number You Just Heard: You ask Businessman ecstatic about the low estimatesomeone how long something will take. They come back to you with an estimate that is about 25% of what you thought it would have taken to complete that activity.You are thrilled! This is way better than you expected.

    You start calculating how the extra time that is saved can be used to catch up some other deliverables that are running behind on the critical path. You start basing your project plan and schedule around this new found good news.

    Watch out…it’s a trap!

    Unless there has been some revolutionary breakthrough in technology that you are not aware of, common sense will dictate that something that used to take much longer will still take that long.

    Resources may not completely understand what is being asked of them. Or, they may have told you what they thought you wanted to hear so they could get back to work. Regardless, it can wreak havoc on your project plan and schedule.

    Reality will soon start to set in and you find that it’s taking much longer than expected. You stopped looking for ‘plan B’ early on because you were so delighted with the low number. You now find yourself scrambling to catch up and making arrangements to get the project plan and schedule on track.

  • You Disagree with a Really Big Number:The opposite of really Disagrees with the big numberliking the small number you hear is really NOT liking the big number you hear.

    You reason to yourself that there is no possible way that something could take as long as this team resource estimated. You then take it upon yourself to put in a lower amount of time in the project plan and schedule.

    Watch out…it’s a trap!

    This only sets you up for some painful conversations later on in the project when the deliverable ends up taking as long as originally estimated. Team members will wonder why you didn’t take their word for how long it would take. Plus, you have now endangered the project by putting other deliverables on the critical path unnecessarily.

  • You Don’t Push Back:  A final trap to be on the lookout for when it comes to putting your project plan and schedule together, is not questioning either of the numbers above. You just ask a question of how long something will take and then put whatever number they gave you in the project plan and schedule.Watch out…it’s a trap!

    It is entirely within your right and realm of responsibility as a project manager to ask questions. Dig into the details. Challenge assumptions.

    It’s not that you don’t trust the people you work with, you just want to make sure every stone is overturned during the estimating process and that you are all dealing with reality.

    You can ask for a breakdown of what makes up a really long estimate, or ask what is included in a really short estimate. Doing so will make everyone spend a little more time on the estimating process and help ensure the numbers are accurate.

Estimating activity duration for your project plan and schedule is not easy. However, it is an activity that is critical for your projects to end on time. Find the right balance between what you want the numbers to be and the numbers your resources produce. You will find yourself having far fewer conversations that end with “is it really going to take that long??”


One comment

  1. Pingback: Team Charters and Project Plans « Facilitative Leadership & Facilitator Training

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: