Have you ever been on a project where the deadline was way too tight?
Chances are that tempers were frayed, sponsors were unhappy, and team members were working ridiculous hours.
Chances are, too, that this happened because someone underestimated the amount of work needed to complete the project.
People often underestimate the amount of time needed to implement projects, particularly when they're not familiar with the work that needs to be done.
For instance, they may not take into account unexpected events or urgent high priority work; and they may fail to allow for the full complexity of the job. Clearly, this is likely to have serious negative consequences further down the line.
This is why it's important to estimate time accurately, if your project is to be successful. In this article, we look at a process for making good time estimates, and we explore some of the estimating methods that you can use.
Accurate time estimation is a crucial skill in project management. Without it, you won't know how long your project will take, and you won't be able to get commitment from the people who need to sign it off.
Even more importantly for your career, sponsors often judge whether a project has succeeded or failed depending on whether it has been delivered on time and on budget. To have a chance of being successful as a project manager, you need to be able to negotiate sensible budgets and achievable deadlines.
Use these steps to make accurate time estimates:
Start by identifying all of the work that needs to be done within the project. Use tools such as Business Requirements Analysis, Work Breakdown Structures, Gap Analysis and Drill-Down to help you do this in sufficient detail.
As part of this, make sure that you allow time for meetings, reporting, communications, testing and other activities that are critical to the project's success. (You can find out more on these activities in our article on Project Management Phases and Processes.)
Now, list all of the activities you identified in the order in which they need to happen.
At this stage, you don't need to add in how long you think activities are going to take. However, you might want to note any important deadlines. For example, you might need to get work by the finance department finished before it starts work on "Year End."
You can do the estimates yourself, brainstorm them as a group, or ask others to contribute.
Where you can, get the help of the people who will actually do the work, as they are likely to have prior experience to draw upon. By involving them, they'll also take on greater ownership of the time estimates they come up with, and they'll work harder to meet them.
You're now ready to make your estimates. We've outlined a variety of methods below to help you do this. Whichever methods you choose, bear these basic rules in mind:
The most reliable estimates are those that you have arranged to be challenged. This helps you identify any assumptions and biases that aren't valid.
You can ask team members, other managers, or co-workers to challenge your time estimates.
We'll now look at different approaches that you can use to estimate time. You'll probably find it most useful to use a mixture of these techniques.
How much detail you go into depends on the situation. However, the more detail you go into, the more accurate you'll be.
If you don't know how far to go, consider breaking work down into chunks that one person can complete in half a day, for example. Sure, this is a bit circular, but it gives you an idea of the level of detail you should aim for.
Don't assume that the bottom-up estimates are wrong if they differ widely from the top-down ones. In fact, it's more likely that the reverse is true.
Once you've estimated the time needed for each task, you can prepare your project schedule. Add your estimates to the draft activity list that you produced in the second step, above.
You can then create a Gantt Chart to schedule activities and assign resources to your project; and to finalize milestones and deadlines.
You need to estimate time accurately if you're going to deliver your project on time and on budget. Without this skill, you won't know how long your project will take, and you won't be able to get commitment from the people required to help you achieve your objective.
More than this, you risk agreeing to impossibly short deadlines, with all of the stress, pain, and loss of credibility associated with this.
To estimate time effectively, follow this four-step process:
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