Your total stack height will depend on the thickness of your top drive. The rest of your stack will be approximately 12mm per drive when using 7mm thick drives or approximately 14mm per drive when using 9mm thick drives.
To get a better idea of the dimensions of your stack you can multiply 12mm or 14mm by your total number of drives minus 1, then add the height of your top drive (usually either 7mm or 9mm).
Example: 5 stacked drives would result in roughly 65mm total height for the 9mm 5x5 Stackers/Toppers, and approximately 55mm in height for the 7mm 5x5 Stackers/Toppers.