How Commercial Estimator Calculates Costs

Commercial Estimator calculates costs at the component level for each section of an estimate. These costs print in two types of reports:

Detailed Report:	Contains a separate listing for each section of a report with the calculated costs for each construction system in that section.
Summary Report:	Contains the total cost for all components within each construction system (walls, heating/cooling, etc.) in all sections of a report.

The following discusses the three cases where the Number of Units times the Unit Costs may not equal the Total Cost in the report: Multiple Components in a Construction System, Multiple Sections in an Estimate and the Report Subtotals.

Multiple Components in a Construction System

When you have more than one component in a construction system, the Summary Report contains the Total Cost for all these components. It also contains a Unit Cost, which is this Total Cost divided by the Total Number of Units, rounded to the nearest cent. Because of this rounding, the Number of Units times the Unit Cost may not equal the Total Cost, but the Total Cost is an exact total of the individual component Total Costs.

Example: The following are the costs for two walls in a building:

	Units	Unit Cost	Total Cost
Block with Stucco	12,914	14.47	186,866
Brick with Block Back-up	8,610	15.81	136,124

For each component, the Number of Units times the Unit Cost equals the Total Cost (12,914 times $14.47 equals $186,866, and 8,610 times $15.81 equals $136,124).

The sum of these two components prints in the Summary Report as follows:

	Units	Unit Cost	Total Cost New	Less Depreciation	Total Cost Depreciated
Basic Structure
Exterior Walls	21,524	15.01	322,990		322,990
Basic Structure Cost	21,524	15.01	322,990		322,990

The items here are calculated as follows:

Number of Units:	Sum of the Number of Units for these two wall components in the Detailed Report (12,914 plus 8,610 equals 21,524).
Total Cost:	Sum of the Total Costs for these two wall components ($186,866 plus $136,124 equals $322,990).
Unit Cost:	Total Cost divided by the Total Number of Units, rounded to the nearest cent ($322,990 divided by 21,524 equals $15.00604, which rounds to $15.01). Since the Unit Cost was rounded to the nearest cent, the Number of Units (21,524) times the Unit Cost ($15.01) equals $323,075, which is not the Total Cost printed in the Summary Report.

This illustrates that it is often not possible to have the Total Cost in the Summary Report be both the sum of the Total Costs for each component in the Detailed Report and the product of Number of Units times the Unit Cost. In cases like this, we have chosen to have the Total Cost in the Summary Report be the sum of the component costs from the Detailed Report.

Multiple Sections in a Report

Similarly, when you have more than one section in an estimate, the Summary Report contains the Total Cost for all sections for each construction system. It also contains a Unit Cost, which is this Total Cost divided by the Total Number of Units, rounded to the nearest cent. Because of this rounding, the Number of Units times the Unit Cost may not equal the Total Cost, but the Total Cost is an exact total of the individual component Total Costs. This can occur when you have multiple sections in a report, even if you only have one component in a construction system in each section.

Example: The following are the Exterior Wall components in a Detailed Report with two sections:

Section 1

	Units	Unit Cost	Total Cost New	Less Depreciation	Total Cost Depreciated
Basic Structure
Exterior Walls	16,363	15.14	247,736		247,736
Basic Structure Cost	16,363	15.14	247,736		247,736

Section 2

	Units	Unit Cost	Total Cost New	Less Depreciation	Total Cost Depreciated
Basic Structure
Exterior Walls	13,808	14.90	205,739		205,739
Basic Structure Cost	13,808	14.90	205,739		205,739

The total of the two sections prints in the Summary Report as follows:

	Units	Unit Cost	Total Cost New	Less Depreciation	Total Cost Depreciated
Basic Structure
Exterior Walls	30,171	15.03	453,475		453,475
Basic Structure Cost	30,171	15.03	453,475		453,475

The items on this line are calculated as follows:

Number of Units:	Sum of the Number of Units for all wall components in all sections of the Detailed Report (16,363 plus 13,808 equals 30,171).
Total Cost:	Sum of the Total Costs for all wall components in all sections of the Detailed Report ($247,736 plus $205,839 equals $453,475).
Unit Cost:	Total Cost divided by the Total Number of Units, rounded to the nearest cent ($453,475 divided by 30,171 equals $15.03016, which rounds to $15.03). Since the Unit Cost was rounded to the nearest cent, the Number of Units (30,171) times the Unit Cost ($15.03) equals $453,470, which is not the Total Cost printed in the Summary Report.

Report Subtotals

Both the Summary Report and the Detailed Report have subtotals at various points in the report (Basic Structure Cost, Total Superstructure Cost, Replacement Cost New, Depreciated Cost, etc.). In these subtotals, the Total Cost is the exact total of the costs for all construction systems up to that point. The Unit Cost in the subtotal line is this Total Cost divided by the Total Floor Area of the Building (or the Section in a Detailed Report), rounded to the nearest cent. Because of this rounding, the Number of Units times the Unit Cost may not equal the Total Cost.

Example: The following are the Construction System lines and the Basic Structure Cost in a Summary Report:

	Units	Unit Cost	Total Cost New	Less Depreciation	Total Cost Depreciated
Basic Structure
Base Cost	10,000	64.83	648,300		648,300
Exterior Walls	10,000	16.94	169,400		169,400
Heating & Cooling	10,000	6.77	67,700		67,700
Elevators	1	41,040.00	41,040		41,040
Sprinklers	10,000	2.61	26,100		26,100
Basic Structure Cost	10,000	95.25	952,540		952,540

The items on the Basic Structure Cost line are calculated as follows:

Number of Units:	Total Floor Area of the estimate (or of the Section in a Detailed Report).
Total Cost:	Sum of the Total Costs for each of the construction systems (Base Cost, Exterior Walls, Heating & Cooling, Elevators and Sprinklers: $648,300 plus $169,400 plus $67,700 plus $41,040 plus $26,100 equals $952,540).
Unit Cost:	Total Cost divided by the Number of Units, rounded to the nearest cent ($952,540 divided by 10,000 equals $95.254, which rounds to $95.25). Since the Unit Cost was rounded to the nearest cent, the Number of Units (10,000) times the Unit Cost ($95.25) equals $952,500, which is not the Total Cost printed in the report.