Revit Total Areas & Rounding Issues
Overview
When working with Revit areas, either through an area scheme or architectural rooms, it's common to create a schedule of those areas, and utilize the auto-calculation aspect of Revit to get the totals of the floor/department/etc.
Problem
If you interrogate your list of rooms, occasionally you will notice that the rounded values presented in the schedule end up not adding up to the totals presented in the schedule. There ends up being a discrepancy between some values, which can cause issues for clients or in planning.
Example
To illustrate and discuss what is happening, we will use this example. Presented here are 4 rooms that were created in Revit, and the values associated with the rounding created in a schedule from Revit. Each column B through F was set to the Area of the space/room, with different rounding precision for each (0 decimals, 1 decimal, etc)
Maximum Precision - Column F
While we have read elsewhere that Revit stores 15 decimals for numbers, it only lets you schedule up to 12 decimals for the Area in a Room or Area schedule (done by “custom” with .000000000001 precision).
Therefore, we are stating that 12 decimals is the “maximum precision” you can get in an Area/Space; and when we discuss the “most precise” area measurement, this is the precision we are talking about (column F).