VBA Constants (Const)


Example

If you have a value that never changes in your application, you can define a named constant and use it in place of a literal value.

You can use Const only at module or procedure level. This means the declaration context for a variable must be a class, structure, module, procedure, or block, and cannot be a source file, namespace, or interface.

Public Const GLOBAL_CONSTANT As String = "Project Version #1.000.000.001"
Private Const MODULE_CONSTANT As String = "Something relevant to this Module"

Public Sub ExampleDeclaration()    

    Const SOME_CONSTANT As String = "Hello World"
    
    Const PI As Double = 3.141592653

End Sub

Whilst it can be considered good practice to specify Constant types, it isn't strictly required. Not specifying the type will still result in the correct type:

Public Const GLOBAL_CONSTANT = "Project Version #1.000.000.001" 'Still a string
Public Sub ExampleDeclaration()

    Const SOME_CONSTANT = "Hello World"           'Still a string
    Const DERIVED_CONSTANT = SOME_CONSTANT        'DERIVED_CONSTANT is also a string
    Const VAR_CONSTANT As Variant = SOME_CONSTANT 'VAR_CONSTANT is Variant/String
    
    Const PI = 3.141592653        'Still a double
    Const DERIVED_PI = PI         'DERIVED_PI is also a double
    Const VAR_PI As Variant = PI  'VAR_PI is Variant/Double
    
End Sub

Note that this is specific to Constants and in contrast to variables where not specifying the type results in a Variant type.

While it is possible to explicitly declare a constant as a String, it is not possible to declare a constant as a string using fixed-width string syntax

'This is a valid 5 character string constant
Const FOO As String = "ABCDE"

'This is not valid syntax for a 5 character string constant
Const FOO As String * 5 = "ABCDE"