Overlap of one floor with the staircase

My question is, how large can this overlap be? For the staircase, I assume a length of 4.0 m.
A drawing for better understanding is attached.

It cannot be answered generally, as it depends on the floor construction, story height, and degree of the staircase.
Simply plan without overlap. As a layperson, you can’t really plan to a precision of a few centimeters anyway.
If necessary, when the planner finalizes everything, you can be pleasantly surprised by a bit of excess. For perfect furniture transport, I recommend not building at all.

google: Stairs 101

Draw the staircase in side view in a reduced scale. Keep in mind that a person swings their leg while walking. There should be at least 2m of clear height here.

I simply assume "standard" for the story height. So about 2.6 m

That is not standard - at best in BW. A room height of about 260 cm is considered standard, and thus a story height of about 285 cm.

What do you mean by the chicken ladder?

285 : 16 risers = 17.81 cm step height = 27.38 cm tread depth x 16 = 4.38 m staircase length. With 15 risers 19/26 it would be only 3.90 m, but that would only be considered comfortable up to about forty. With your 4 m staircase length, one would not look forward to retirement – one would rather sing "if only I were seventeen again ..."

Maybe you understand the problem better this way:


Here the overlap is a good 50 cm. And it already becomes uncomfortable if you are 180 cm or taller.

If you come down the stairs with a bit of momentum, it can even become a problem for smaller people.