Visual Basic for Applications:
Rounding numbers

How to:

In Visual Basic for Applications (VBA), rounding can be achieved using several functions, each suited for specific scenarios. Here are the most commonly used functions with examples:

1. Round Function: The Round function rounds a number to a specified number of digits.

   Dim roundedNumber As Double
   roundedNumber = Round(3.14159, 2)  ' Output: 3.14
   MsgBox roundedNumber

2. Int and Fix Functions: Both Int and Fix functions are used to round down numbers to the nearest integer, but they behave differently with negative numbers.

   Dim intRounded As Integer
   Dim fixRounded As Integer
   
   intRounded = Int(-3.14159)  ' Output: -4
   fixRounded = Fix(-3.14159)  ' Output: -3
   
   MsgBox "Int: " & intRounded & ", Fix: " & fixRounded

3. Ceiling and Floor Functions: VBA lacks built-in Ceiling and Floor functions found in other languages. To simulate this, use Application.WorksheetFunction.Ceiling_Math and Application.WorksheetFunction.Floor_Math for Excel VBA.

   Dim ceilingNumber As Double
   Dim floorNumber As Double
   
   ceilingNumber = Application.WorksheetFunction.Ceiling_Math(3.14159)  ' Output: 4
   floorNumber = Application.WorksheetFunction.Floor_Math(3.14159)  ' Output: 3
   
   MsgBox "Ceiling: " & ceilingNumber & ", Floor: " & floorNumber

Deep Dive

The Round function in VBA is inherently different from rounding methods in other languages due to its use of Banker’s Rounding. Banker’s Rounding rounds to the nearest even number when exactly halfway between two numbers, reducing bias in calculations over a large dataset and providing a more statistically significant result. However, this can lead to unexpected behavior for those unfamiliar with it, especially when integral precision is expected in every case.

In contrast, many programming languages and systems use “arithmetic rounding” or “half-up rounding,” where a number exactly halfway between two possible rounded values is always rounded up. When translating or porting code from other languages to VBA, programmers must keep these differences in mind to avoid subtle bugs or inaccuracies in financial and statistical applications.

While VBA offers a variety of functions for rounding, the absence of Ceiling and Floor functions (without resorting to Excel’s WorksheetFunction) highlights a limitation in its native capabilities. Programmers coming from more feature-rich languages might find these omissions inconvenient and might need to implement custom solutions or adapt their calculations to use available functions. Despite these limitations, understanding and using VBA’s rounding functions correctly can help ensure that numerical computations are both accurate and meet the requirements of most applications.