Optimally plan sloping cheek staircase

Hello everyone,

we are planning a straight stringer staircase in our house, which is supposed to span a height of 250 cm from the ground floor to the upper floor.

Our architect has planned an opening in the ceiling of 330 cm for this.

Now my question:
How large/long should this opening be so that the staircase is comfortable to use / walk on?

We have a step height of 18cm and 17 steps. This bridges a floor height of 306cm, including the upper floor ceiling (2.70cm room height + 36cm upper floor ceiling). Our staircase is about 4.30cm long and comfortable to walk on; I wouldn’t make it steeper. Yours seems too short to me, your rooms are only 20cm lower.

Best regards Sabine