Primavera P6 Top-Down Estimating is a function that is typically used to help with high-level resource planning. The Top-Down Tool in Primavera P6 allows users to perform high-level top-down estimation for labor, non-labor units, and material resources for a project.
If you have an idea of the total hours a resource will be working on a project, then you can allocate the proportion of hours that resource will be assigned to their work packages and tasks.
The Primavera P6 Top-Down Estimating offers users two different estimating methods; Prior Experience and Function Point.
Prior Experience Top-Down Estimating Using Primavera P6
Prior top-down estimating is the most commonly used method. As the name suggests it based on prior experience or historical data. The Project Manager or a project team that has completed a similar project will offer their insights on the information required to perform the Top-Down Estimation. This historical data will allow the user to make a successful Top-Down Estimation.
Function Point Top-Down Estimating Using Primavera P6
This method is mainly used for information technology projects. Algorithms and other specialist calculations are used to measure resource units.
Primavera P6’s estimating tool works in two fairly easy steps; firstly, users need to determine the total number of resources to apply, secondly estimation weights are assigned to the Work Breakdown Structure (WBS) elements and individual activities. The Top-Down Estimation Tool will then distribute the resource units (hours) from the ‘top’ WBS elements ‘down’ to the activities.
In our ‘Pipe Repair’ project, we haven’t assigned any resources, as shown below in Figure 1. We are going to perform a top-down estimate of the entire project.
First, we look at the Work Breakdown Structure (WBS) for our ‘Pipe Repair’ project by selecting the ‘WBS’ tab as displayed in Figure 2.
We select ‘Columns’ and in the ‘Find’ dialog box we type in ‘Est weight’ and search until we can select the ‘Est Weight’ selected option as shown in Figure 3.
Once selected we add the ‘Est Weight’ and the ‘At Completion Total Cost’ columns to the WBS, as shown in Figure 4.
The ‘Est Weight’ of piping and thrust block adds up to the installation piping system deliverable.
All of the deliverables, (‘Demolition Piping’, ‘Installation Piping System’, and ‘Quality Assurance’) add up to an ‘Est Weight’ of 9.0. The total ‘Est Weight’ of the project is 10.0. This is done so that we can distribute some of the costs to our high-level project management effort.
We add the columns: ‘Est Weight’, ‘Budgeted Labor Units’, ‘Budgeted Labor Cost’, and ‘Budgeted Total Cost’, to the activity table as shown in Figure 5.
All our weights are now distributed among deliverables and activities. The ‘Est Weight’ of activities add up to the ‘Est Weight’ of the associated deliverables displayed in Figure 4.
Next, we add a lump sum of $100.00/h resource into our resource database as displayed in Figure 6.
In Figure 7, our schedule is displayed after we have assigned the lump sum resource to all of the activities.
In the top ribbon, we select ‘Tools’ and from the drop-down menu, we select ‘Top-Down Estimation’ as shown in Figure 8.
In the ‘Top-Down Estimation’ dialog box, we enter the ‘Activities To Estimate’ section, and in the ‘WBS’ we select the project top level. In ‘Resource’ we select ‘lumpsum’. In the ‘Estimated Section,’ we toggle on ‘Prior Experience’, and in the ‘Estimated Units’, we enter a 600-hour effort for the entire project, as shown in Figure 9.
After we click ‘Apply’ to our ‘Top-Down Estimation’ we review how our estimated 600-hour effort has been distributed between our activities and deliverables as shown in Figure 10.
We review the WBS, as it correlates to the activities table, as shown in Figure 11.
We are content with our Top-Down Estimation and decide to save it for future reference. We return to the ‘Top-Down Estimation’ dialog box and select our WBS, resource, and our (600-hours) estimated units and click ‘Save As’ and In the ‘Estimate Name’ box we enter our Top-Down Estimate as ‘Lum Sum 600-hr’ and click Save, as shown in Figure 12.
Our Top-Down Estimation is automatically saved in our ‘Estimation History’ as shown in Figure 13.
We want to investigate the impact of a minor 10 % percentage adjustment increase on the estimated units, as shown in Figure 14.
We review the Top-Down Estimate with a 10% increase in our budgeted labor units as shown in Fig 15.
Using the Top-Down Estimation history, we could save this new estimate for future reference.
Top-Down Estimating in Primavera P6 can be used to quickly assign the budgeted hours for your resources if you know the proportion of how the hours that should be spread over the work packages and activities.
Performing a Top-Down Estimation is a fairly easy process; your estimation will be more accurate if your activity weights add up to your deliverable associated estimated weights. Primavera P6 allows you to add an incremental percentage adjustment on your estimated units and review the results.
By storing your top-down estimation in your history you can use it as a reference for future projects.