Basic Sum symbols + Add Subtract / Divide * Multiply

Formulas can be very useful to enable a Content creator to (1) establish relationships between Family parameters and (2) to lock in a definite Parameter value.

E.g. 5 Panel window with Awning panel on each end and three centre panels that are equal in width.

Note: Usually once a formula has been entered the Parameter name becomes ghosted and is no longer directly editable in the Project file or from the value cell in the Type menu. (As shown above)

With formulas the following rules apply:

There should be a space between each parameter and the sum E.g. Parameter(space)+(space)Parameter = A + B

Parameter names are case and spelling sensitive. Match the parameter name exactly.

  • If you create a formula to lock a value of a Parameter, as shown above (Awning Panel Width = 900mm) then this value will be locked for ALL types within the family. This is a good idea for values that should be consistent across types. E.g. if you are creating a suite of windows and you want all suite frame depths to be 150mm.
  • Enclose separate sums with brackets. E.g. As seen above in Centre Panel Width = (Sum 1) / 3
  •  Instance Parameters cannot be included in formulas to determine the value of a parameter that is a Type parameter
  •  Revit Help menu has some more complex “IF”, “AND” and “Yes/No” formulas listed

© Copyright Reserved by Michelle Louw (Excerpt from My speaker notes at National Revit Technology Conference 2008.)



  • I find it best to plan what my users may need so that I can avoid content creators creating their own Shared Parameters in their own files. I find it works best if one person is the author of the file and redistributes it to all Content creators and Revit® Managers (If more than one office/ Interstate etc.) when changes are made. Establish an office naming convention and keep it consistent.
  • Avoid using symbol “–“ in the Parameter name because that will affect your formula options. (E.g. Panel – Width) In the formula field this dash will become a minus. (Suggestion: Panel_Width)
  • I like to name SP’s so that they sort in a logical order. See Screenshot example. It’s easy to pick any panel SP that may exist or identify a missing one.
  • Useful Parameters to add to a family are ( “Addenda”, ”Made By”, “Edited by” and “Note to User”) “Note to user” allows you to put comments for user.(E.g. Max 4 panels)
  • Parameters that users will often need to be referred to in the Project file can be grouped under “Constraints” or “Construction” to make editing these values in the Project or Family file quick and easy.

© Copyright Reserved by Michelle Louw (Excerpt from My speaker notes at National Revit Technology Conference 2008.)


Shared Parameters are invaluable if you intend to schedule any custom parameter values now or in the future from a Project file. Predicting what you may wish to schedule will give you a good idea of how to define the parameters, constraints and labels to give you the data output that you may need. Here is an example of what can be scheduled using SP’s. (Note the Column headings in the schedule can be renamed.)


  • Make sure all content creators in your company are using the identical copy of the Shared Parameters (SP) text file.
  • PITFALL. Making the same Shared Parameter in your own local SP file will not be the same as using the official Office SP file. Essentially parameters that originate from two different SP files are given different data identifiers and therefore Revit® will see them as different from one another, even though they may be identical in every other way. As a result you will end up with duplicate parameters in a Project file that will schedule separate SP data. Unfortunately there is no workaround for this. To solve this problem you will need to swap out the uncertified SP’s (that originated from other SP file) from the affected families and replace those SP’s with the approved SP’s (that are being used in the Project schedule) from the official Office SP file and reload the amended families into the Project file.

Remember to only add specific SP’s into the Project files / Office Template that you wish to schedule (Only tick affected Family categories.)

© Copyright Reserved by Michelle Louw (Excerpt from My speaker notes at National Revit Technology Conference 2008.)