Re: formula to calculated area if yes/no

You're on the right track! Using a conditional statement within a Revit formula is precisely how you'd achieve this. Revit formulas support a simple IF function that's perfect for this scenario. Here's the breakdown:

The Formula:

IF(Yes/No Parameter, Height * Width, 0)

Explanation:

• IF(condition, result_if_true, result_if_false): This is the core of the formula. It evaluates the condition. If the condition is true, it returns result_if_true. Otherwise, it returns result_if_false.
• Yes/No Parameter: Replace this with the exact name of your Yes/No parameter. Revit formulas are case-sensitive, so double-check the spelling.
• Height * Width: This is your area calculation. Make sure Height and Width are also the exact names of your length parameters.
• 0: This is what happens if the Yes/No parameter is not checked (i.e., "No"). You could use a different value here if you wanted something other than zero when the condition is false (e.g., a default area, or even another formula).

Example in Revit:

Let's say your parameters are named:

• CalculatedArea (Area parameter)
• CalculateArea (Yes/No parameter)
• ElementHeight (Length parameter)
• ElementWidth (Length parameter)

Your formula for the CalculatedArea parameter would be:

IF(CalculateArea, ElementHeight * ElementWidth, 0)

How it Works:

1. Parameter Setup: Ensure you've created all four parameters (Area, Yes/No, Length, Length) and assigned them to the appropriate family category.
2. Formula Input: In the family editor, select the element to which these parameters are assigned. Go to the Family Types dialog. Find your CalculatedArea parameter. In the formula field for this parameter, paste the formula.
3. Testing: Load the family into a project. Select an instance of the family. In the Properties palette, check and uncheck the CalculateArea Yes/No parameter. You should see the CalculatedArea update accordingly.

Important Considerations:

• Units: Revit formulas are unit-aware. Ensure your Length parameters (ElementHeight, ElementWidth) are using consistent units. The resulting Area will be in the square of those units.
• Case Sensitivity: Revit parameter names in formulas are case-sensitive. Double-check the names.
• Formula Syntax: Be precise with your syntax. Commas are essential.
• Parameter Types: Make absolutely sure your parameters are of the correct type (Area, Yes/No, Length). A mismatch will cause the formula to fail.
• Nested IFs: You can nest IF statements for more complex logic. For example, if you wanted different calculations based on other conditions. However, keep it as simple as possible for maintainability.
• Shared Parameters: If you need this functionality across multiple families, consider using shared parameters.

Example with a Default Area:

Let's say you want a default area of 10 square meters when CalculateArea is "No." Assuming your length units are meters, your formula would be:

IF(CalculateArea, ElementHeight * ElementWidth, 10)

This will calculate the area based on height and width if CalculateArea is "Yes," and will use 10 square meters if CalculateArea is "No."

This should give you a solid foundation for controlling area calculations with Yes/No parameters in Revit. If you have further questions, feel free to ask!