Estimates developed during the solution, bid and sales phase of any engagement must be reconfirmed when the engagement actually commences. Things change over time (scope, assumptions, dependencies, resource costs, etc.) and any changes must be identified in order to effectively and accurately manage the timescales and costs going forward.
Accurate time estimation is a crucial skill in project management. Without it, you will not know how long your project will take, and you will not be able to get commitment from the people who need to sign it off.
Even more importantly, 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.
Understand what is required
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.
Order these activities
Now, list all of the activities you identified in the order in which they need to happen. At this stage, you do not need to add in how long you think activities are going to take. However, you might want to note any important deadlines.
Decide whom you need to involve
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 will also take on greater ownership of the time estimates they come up with, and they will work harder to meet them.
Make your estimates
You are now ready to make your estimates. We have outlined a variety of methods below to help you do this. Whichever methods you choose, bear these basic rules in mind:
- To begin with, estimate the time needed for each task rather than for the project as a whole.
- The level of detail you need to go into depends on the circumstances.
- List all of the assumptions, exclusions and constraints that are relevant. This will help when your estimates challenged, and will help you identify any risk areas if circumstances change.
- Assume that your resources will only be productive for 80 percent of the time. Build in time for unexpected events such as sickness, supply problems, equipment failure, accidents and emergencies, problem solving, and meetings.
- If some people are only working part-time on your project, bear in mind that they may lose time as they switch between their various roles.
- Remember that people are often overly optimistic, and may significantly underestimate the amount of time that it will take them to complete tasks.
- Verify validity of original solution scope.
- Validate dependencies and assumptions.
- Validate resource estimates.
- Resolve discrepancies through appropriate change control.
- Crosscheck estimates with experiential rules of thumb.
- Establish cost management process.
Hints and tips
- Estimating is a key skill. Ensure the necessary expertise applied and brought into the project.
- Always use two estimating techniques to crosscheck results.
- Use the project labor cost estimator.