Parametric Modeling and Valid Formula Syntax and Abbreviations within Revit

Valid Formula Syntax and Abbreviations

Formulas support standard arithmetic operations and trigonometric functions.

Formulas support the following arithmetic operations: addition, subtraction, multiplication, division, exponentiation, logarithms, and square roots. Formulas also support the following trigonometric functions: sine, cosine, tangent, arcsine, arccosine, and arctangent.

The valid formula abbreviations for arithmetic operations and trigonometric functions are

• Addition— +
• Subtraction— -
• Multiplication—*
• Division—/
• Exponentiation—^: x^y, x raised to the power of y
• Logarithm—log
• Square root—sqrt: sqrt(16)
• Sine—sin
• Cosine—cos
• Tangent—tan
• Arcsine—asin
• Arccosine—acos
• Arctangent—atan
• 10 raised to an x power—exp(x)
• Absolute Value—abs
• Pi—pi (3.1415926...)

You can enter integers, decimals, and fractional values in formulas, using normal mathematical syntax, as shown in the examples below:

• Length = Height + Width + sqrt(Height*Width)
• Length = Wall 1 (11000mm)+ Wall 2 (15000mm)
• Area = Length (500mm) * Width (300mm)
• Area = pi() * Radius ^ 2
• Volume = Length (500mm) * Width (300mm) * Height (800 mm)
• Width = 100m * cos(angle)
• x = 2*abs(a) + abs(b/2)
• ArrayNum = Length/Spacing

You can use the round function for values in formulas. 

Function syntax	Description	Examples
round(x)	The round function returns a value rounded to the nearest whole number. It doesn't take into consideration rounding direction.	round(3.1) = 3 round(3.5) = 4 round(-3.7) = -4
roundup(x)	The roundup function returns a value to the largest integral value greater than or equal to x.	roundup(3) = 3 roundup(3.1) = 4 roundup(-3.7) = -3
rounddown(x)	The rounddown function returns a value to the smallest integral value less than or equal to x.	rounddown(3) = 3 rounddown(3.7) = 3 rounddown(-3.7) = -4

 

Parameter names in formulas are case sensitive. 

 For example, if a parameter name begins with a capital letter, such as Width, you must enter it in the formula with an initial capital letter. If you enter it in a formula using lower-case letters instead, for example, width * 2, the software will not recognize the formula. 

Note: It is recommended that you do not use a dash (-) when naming parameters. From Autodesk's Help Network Site