How does “Top Down Estimation” in Primavera P6 work?

Primavera P6 includes a feature called Top-Down Estimation, which helps calculate estimated labor and non-labor units based on estimation weights. This method can be applied at both the WBS and Activity levels to distribute units more realistically.

Scenario

We have a simple project where each activity is assigned the resource Test, and by default, each activity has 40 units.
We’ll use Top-Down Estimation to redistribute these units according to estimation weights.

Step 1: Assign Estimation Weights

Before performing top-down estimation, you must assign Estimation Weights to WBS elements and activities. These weights determine how units are distributed.

• Go to the WBS window and display the Est Weight column.
• Enter weights for each WBS element.
• Then, go to the Activities window, display the Est Weight column, and enter weights for each activity.

Enter the weight for each WBS.

Go to Activities window. Show “Est Weight” column.

Enter the weight for each activity.

Step 2: Perform Top-Down Estimation

1. Go to Tools → Top-Down Estimation.
2. Primavera will display the current units in your project.
3. Enter the new total units you want to apply to the project.
4. Click Apply.

Primavera will redistribute units across WBS and activities based on the estimation weights you assigned.

Click on Apply button.

Now you can see WBS and activities have new budgeted units.

The units are distribute according to Est Weight which we assigned to them.

If the total units are 1,000:

• Foundation WBS has 40% weight → 400 units.
• Bored Pile activity under Foundation has 70% weight → 280 units.

Key Benefit

This feature allows you to quickly and accurately distribute units across your project based on relative importance or complexity, without manually adjusting each activity.