The dimensions permitted for Ryanair's small hand luggage are 35x20x20. An Eastpak backpack is about 45x38x11. Will it be allowed on board? Please refer your personal experiences on this subject.
EDIT: What if I carry it nearly empty and folded into 2 parts, so that it'll fit? (I really need to take a backpack with me, but there's no room in my other luggage, that's why I'm asking these questions)
45x38x11 cm is above the size that Ryanair say they will definitely allow in the cabin (35x20x20 cm) but below the maximum size of hand luggage (55x40x20 cm) so if it's your only piece of hand luggage you might be allowed to take it on, and if not it will be carried in the hold for free.
In my experience, when they insist that passengers gate check their luggage they are mainly looking for the big wheely suitcases which just fit in the cage at all. The main limitation is on overhead locker space, so if your bag looks like it will fit under the seat in front of you then you're probably OK.
It is over the size in two dimensions. It will not fit in the measuring frame. And I have never heard that Ryanair would allow anything that might bring them money when they keep to the rules.
I would not risk it, the best you can expect is gate checking for free, the worst is a big fee for check-in luggage that has not been announced by internet.
I have seen a single stick being denied entry into a plane as oversize while it did fit in the case on a diagonal.
