Quick Quantities using Field Conversion Factors

The long list of inquiry tools within AutoCAD provide many ways to approach the task of performing quantity takeoffs on your drawings. Yet as powerful as these tools are, one limitation that has long challenged me is way 1 doesn’t always equal 1 in the context of quantity takeoffs. A common example of this is the need to calculate the number of parking stalls throughout a site. Because of site design elements such as parking islands, it’s likely some stalls will not have a painted stripe separating it, meaning it’s not necessarily possible to get an accurate count by simply calculating the number of paint striping lines in my drawing.

Despite this limitation, one consistent parameter with parking stalls is their width. It stands to reason that an accurate count could be achieved by adding up the length of a parking stall run, and dividing it by the width of a single stall. Interestingly enough, this can be automated using a lesser known Conversion Factor parameter for Fields.

Creating the Field

Above I have a simple parking lot layout, for which I need to calculate the number of stalls within each of its three distinct runs. We’ll start with the run on the left by creating a Field that will calculate the total number of parking stalls:

1. First I need to establish the typical parking stall width. Using the DISTANCE command, I learn this value is 8′ 10-1/4″ (106.25 inches).
2. We need something to link the Field we’ll create in a moment. I’ll draw a simple Line spanning the entire run of parking stalls to serve this function.
   
3. With this line in place I’ll insert my standard parking count block.
   It’s worth noting that its also possible to use Multiline Text , however I find Block Attributes to be the better choice since they are compatible with Data Extraction tables (that could be used to calculate a site total).
4. Within the Edit Attributes dialog, right-click inside the textbox for your parking count attribute, and choose Insert Field.
   
5. From the Field dialog, change Field Category to Objects; select Object from the Field Names list; and finally click the Select Object button next to the Object Type textbox.
   
6. At the Select Object: prompt, select the parking run reference line created in step 2.
7. Once returning to the Field Dialog, select Length as the Property, and Decimal as the Format.
   
8. Open the Additional Format dialog by clicking the Additional Format… button in the right column of the Field dialog.
9. Calculate the Conversion Factor by dividing 1/106.25. Enter the result into the Conversion Factor text box.
   
10. To ensure an even number like 10 instead of 10.00, check the Leading and Trailing checkboxes for Zero Suppression. Click OK.
11. Likewise, to prevent AutoCAD from reporting partial parking stalls, change the Precision to 0, and click OK twice (to exit the Field and Edit Attributes dialogs)
    
12. The Parking Count block is placed into your drawing, reporting the correct count of parking stalls.
    

Counting Additional Runs

With the first run complete, additional runs are easy to calculate. Using the COPY command to copy both the block (field) and reference line will automatically associate the new block (field) with the new reference line.

1. Start the COPY command and select both the Reference Line and the Parking Count block (field). AutoCAD will not create a new link unless both the reference line and Parking Count block (field) are selected at the same time.
   
2. After creating a copy of the original Field/Reference Line combination, use Grips to adjust the new Reference Line.
   
3. If the Field doesn’t automatically update after adjusting the new Reference Line, enter REA to execute the REGENALL command. The parking count updates: