dual boot: partition by default how many disk space?

[ubu-lemon]

I wonder how much disk space a non manual dual boot uses?

I've always been guided by a person knowing much about linux when doing my dual boot (and been guided to do the partitions manualy), but this person is not there for the moment and I need to do a dual boot on my son's computer.

Since he'll need his Windows computer mainly for games I wouldn't want Ubuntu to take 2/3 of his disk space (which is about 250 Gb I think, let's say 50 Gb would be perfect for the Ubuntu)

And I'm not sure how I could change this later, cause in my own computer I cannot find how to resize (I cannot unmount neither resize the partitions I have) I don't mean I need to do this on my computer but I mean I wouldn't want to try out anything if I'm not sure it be could restored in 1,2,3.
And partitions is such a thing.
If I remember correctly I've done dual boot by default (i mean without doing the partitions manualy) and it does about 50/50 ?

thanks for your help
(please bear in mind I'm not a genius linux user, just a simple one with little knowledge)
Sarah.

[pricetech]

a 50/50 split should work just fine, unless you have a compelling reason to have a lot of drive space for one OS or the other. Guided partitioning at install time gives you an easy to understand graphical
representation of your drive space. You shouldn't have any problem.

[ubu-lemon]

you mean that except manual and default, there is also the option to have a 'guided' partitioning?
(50/50 is far too much, it's not my computer, it needs to keep 3/4 for Windows)