Integer variables are stored as 16-bit (2-byte) numbers
Office VBA Reference
Long (long integer) variables are stored as signed 32-bit (4-byte) numbers
Office VBA Reference
So, the benefit is in reduced memory space. An Integer takes up half the memory that a Long does. Now, we are talking about 2 bytes, so it’s not going to make a real difference for individual integers, it’s only a concern when you are dealing with TONS of integers (e.g large arrays) and memory usage is critical.
BUT on a 32 bit system, the halved memory usage comes at a performance cost. When the processor actually performs some computation with a 16 bit integer (e.g. incrementing a loop counter), the value silently gets converted to a temporary Long without the benefit of the larger range of numbers to work with. Overflows still happen, and the register that the processor uses to store the values for the calculation will take the same amount of memory (32 bits) either way. Performance may even be hurt because the datatype has to be converted (at a very low level).
Not the reference I was looking for but….
My understanding is that the underlying VB engine converts integers to long even if its declared as an integer. Therefore a slight speed decrease can be noted. I have believed this for some time and perhaps thats also why the above statement was made, I didnt ask for reasoning.
This is the reference I was looking for.
Short answer, in 32-bit systems 2 byte integers are converted to 4 byte
Longs. There really is no other way so that respective bits correctly line
up for any form of processing. Consider the following
MsgBox Hex(-1) = Hex(65535) ' = True
Obviously -1 does not equal 65535 yet the computer is returning the correct
“FFFF” = “FFFF”
However had we coerced the -1 to a long first we would have got the right
answer (the 65535 being greater than 32k is automatically a long)
MsgBox Hex(-1&) = Hex(65535) ' = False
“FFFFFFFF” = “FFFF”
Generally there is no point in VBA to declare “As Integer” in modern
systems, except perhaps for some legacy API’s that expect to receive an
And at long last I found the msdn documentation I was really truly looking for.
Traditionally, VBA programmers have used integers to hold small
numbers, because they required less memory. In recent versions,
however, VBA converts all integer values to type Long, even if they’re
declared as type Integer. So there’s no longer a performance advantage
to using Integer variables; in fact, Long variables may be slightly
faster because VBA does not have to convert them.
To clarify based on the comments: Integers still require less memory to store – a large array of integers will need significantly less RAM than an Long array with the same dimensions. But because the processor needs to work with 32 bit chunks of memory, VBA converts Integers to Longs temporarily when it performs calculations
So, in summary, there’s almost no good reason to use an
Integer type these days. Unless you need to Interop with an old API call that expects a 16 bit int, or you are working with large arrays of small integers and memory is at a premium.
One thing worth pointing out is that some old API functions may be expecting parameters that are 16-bit (2-byte) Integers and if you are on a 32 bit and trying to pass an Integer (that is already a 4-byte long) by reference it will not work due to difference in length of bytes.
Thanks to Vba4All for pointing that out.