Some Revit Food for Thought – using calculated formulas in Tags.

Tagging elements in Revit is an invaluable way to enhance your documentation. One feature that is not so well known is that you can create your own calculations inside a Tag. So rather that just displaying the raw parameters of an object, you can get the Tag to do a bit of the heavy lifting.

In this example I will use a Tag that shows us the approximate cost of a Wall. To achieve this, we’ll assume that we have a square metre rate and put that into the Cost parameter (a Type Parameter that is built into all Walls) and multiply this by the Area parameter (an Instance Parameter that is built into all Walls).

Cost is a Type Parameter so we create 2 Walls of different Types and then go into their Type Properties and we’ll enter an arbitrary value for that $ per square metre rate.

Since Area is a parameter that is automatically created by Revit when we make or adjust a Wall’s dimensions then we won’t need to do anything for that part of the process.

Now that we’ve done that, we can create a Tag with a calculated value in it to display the total cost of the Walls in our Project.

Go to File > New Family  – now navigate to the Annotations Folder. Note that Revit doesn’t have a complete range of Tag templates so we have to pick a Generic Tag and then tell Revit what Category of objects we want this Tag to apply to. Pick the Template:

First thing we do is to change the category to Wall Tags by clicking on the Family Category and Parameters Icon (above the Family Types Icon):

Now that we’ve done this, we will have access to the parameters of Walls.

If this is the first time you’ve made a Tag then read the red text but always delete the Red Text unless you like random bits of text appearing in your Viewports (I’m guessing not)!

Now go to the Create Tab > Label – and click on a point just above the intersection of the green dashed lines in the viewport. A Label is a special piece of Text that grabs information from an object in the Project and displays it. You find Labels in Titleblock Families as well where for example they show information about the Project.

Now that you’ve clicked on a point on the Viewport, the Edit Label dialogue pops up . This shows a list of all the available Parameters for the particular Category of Tag we have selected.

Note that we can also add custom Parameters to the list on the left hand side by using of a Shared Parameter File (not part of this exercise).

Click on the little formula button:

Now type in a name for the Calculated Value. Pick Currency in this case. While you are there, have a look at the different disciplines and check out the range of Parameters that are available inside Revit (it’s quite a list!).

Now click on the little button with the 3 dots on it:

We will get a dialogue with all the Parameters that are in the list on the left hand side of the Edit Label dialogue (including any custom parameters that we might have loaded).

In the Fields Dialogue box that opens, click on Area. Now type “*” into the window (without the parentheses)

Now click on the little button again and pick Cost.

It will look like this:

At this point, you can try to click on the OK button. If you do you’ll get an error dialogue pop up with an obscure message. This is a “YOU SHALL NOT PASS” moment (straight out of Lord of the Rings). What’s going on here Revit? Well the short answer is that Revit can’t work out the correct units for the result of the equation (what units does $ multiplied by square metres have??).

The good news is it’s easy to resolve. We simply divide of the things by itself. So if we divide $1 by $1 for example. the result is 1 i.e. a value that has no units.

This is what we will type to get past Revit’s warning box –

Click OK and we can move on.

Whilst we’re at it, click on the little icon at the bottom of the Edit Label button that has a little hand with a Hash symbol on it (this gets the prize for the most obscure Icon in Revit). It allows us to manipulate the way that Revit shows the units in the Tag and override the default unit settings in the Project.

When we click on the Units button, we can now untick the button that says “Use project settings”, set rounding to “0 decimal places” (we don’t want to bother with pesky cents) and then make the Unit Symbol “$’.

Now adjust the width of the Label so that it doesn’t scrunch up in the viewport when we use it in the Project by grabbing the blue circles and dragging them outwards. Move the Label if you are not happy with where it is.

As a garnish, lets keep the Label selected and in the Properties window, click on the Edit Type button and then tick on the Show Border button. You can also adjust other properties of the Label as you would a Text Family.

Almost there! Now click on the Load into Project Icon and select the Project that you created before:

Since we are loading a Tag, Revit will make this the active tool so you can click on the example Walls to Tag them. You can of course use the Tag All or Tag by Category tool at any time.

And as we expect with Tags, if we resize the Wall in any way, the Tag updates to show the new cost.

One limitation with this approach is that there is no way to get this calculated Value to show up in your Schedules. Note that this can be acheived by using a similar process to make a Calculated Value inside the Schedule.


I think this might help speed up documentation in some circumstances where it is useful to show more than the simple parametric values of objects in our documents. Have fun!