Recently got a new bike and at the moment its in the lounge, which doesn't go down too well.
I'm thinking of putting dome hooks in the roof of our 'shed' (actually an old air raid shelter) to hang all 3 vertically by the front wheel.

Question is, what width to you think I need to fit 3 hanging bike. One of them has drops if you think that makes a difference.

I think you need a tape measure.

think you might actually have to measure up your bikes and your shed and work it out.
Can you answer this?
Can I fit 4 pairs of shoes in my shoe rack? One of them is a pair of slippers?

Possibly narrower if they don't hang all same way
outers – by front
inner – by rear
adjust hook heights/locations so they don't interfere

you only need the width of the two MTB bars added together. road bike bars are lower as well as narrower so will squeeze between the two MTBs easily.

Fair points about me doing the measuring. Just being lazy really, and often there's strange knowledge about these sort of things floating about here.
I'll do a bit more surveying when I get home.