Cost Estimating: Bottom-Up vs. Top-Down

| Mar 25, 2015


Generating revenue is the light at the end of the project's tunnel, but one of the first steps toward profit is accurate estimating.

Creating a proper estimate involves detailing every expenditure you expect to make throughout the duration of a project. Compiling this information will help you charge the client enough to make a profit on the job, and will also guide you in keeping the project within budget.

Generally, there are two styles of estimating used in home technology installations: bottom-up and top-down. Each entails accounting for each item and labor cost, but there are particular projects and instances where one may be better than the other. It's important to know which method of estimating is best applied depending on the situation.


In this style, project managers tally their costs upward, starting at the bottom and accounting for each expected cost. In sum, the total costs should equal the finished project. It's a basic method of estimating, but the benefit is that it's the most accurate means of estimating a project's total cost. Accuracy is achieved just through the process of starting at the very foundation of a project and working your way up through each cost on the project work breakdown structure.

However, because of the effort needed to detail each and every possible expense – labor, equipment, indirect, direct – using the bottom-up approach is time-consuming. Thus, streamlined and efficient processes are critical in bottom-up estimating, like using standardized work packages and formalized structures.

Bottom-up cost estimating – because of its accuracy – is best applied in large, multifaceted projects. Reining in costs and keeping to a budget is usually critically important in such projects, and bottom-up estimating allows you to work in just that manner.


The top-down approach starts with identifying every major aspect to the project. In home technology installations, you will typically start with the components and features of the job. Then, you will create different labor categories that apply to each task. The cost of the project is measured by estimating how much labor will go into each piece of the job. The set cost of the labor category is multiplied by each relevant task. 

The top-down approach requires a history and knowledge of project pricing to accurately estimate. Smaller-scale installations are commonly the best environment for top-down estimating.

While there is no inherent differentiator or drawback, each method of estimating has its own benefits in certain elements and situations. It's up to you, as the project manager, to know the best method for the best outcome.