A normal pc has an atx form factor and usually has 4 slots. Currently the highest density non ecc ram is 8gb, so 4x8gb=32gb ram. There are x79 boards which are still the same size, atx, but have 8 slots so 64gb ram. There are also atx server boards which can use 32gb sticks for 256gb ram but that's not an average person's pc although it is also not bigger.
Ah okay thank you so much, couldn't for the life of me find any answer like this online and was just killing me