Doesn't matter how large you build it, it still won't be big enough.
When we had to tear down our 150 year old barn, I decided to replace with a nice bank barn/driveshed type of structure. A bank barn structure fits into a hill, and gives you a full height upper/main storey, and a lower height bottom storey that exits the other way.
We ended up with a 28x48 foot building, and - as garages go - it has accumulated stuff over the years. All of my three sons have stuff in there, my wife has stuff in there, there are lawnmowers, snowblowers, weed whackers, old furniture, music equipment, sets of snow tires, etc. and just enough room for my speedster.
No garage is ever big enough...