I unfortunatley don't have a square foot figure as we generally look at the overall site in terms of power and square footage to figure out density, and whether to shrink down or make big depending on what we get.

In respect of our row configurations, lets take two rows, running a hot aisle in the middle with 600mm x 1000mm racks. We have 5 x (600mm x 600mm) tiles for two rows (let's call this R). You would then require at least 2 tiles for working in front of those, so we add another 4 x (600mm x 600mm) to the calculations (lets call this FB).

We also need space to work round the outside as well, for lets add another 2 tiles to the outsides of the row so we can walk all the way round; so we would need 4 x (FB + R).

PS: This is very rough, and should not be taken as gospel as it does not take into account dealing with any plant equipment, H&S, fire exit routes and all that stuff - oh, and I may have made a mistake in my maths somewhere which I probably have