Angles should match the purpose of the stairs. In fact, that is the most important thing before starting the construction. Usually, the constructors know what to do immediately after they are faced with the project. Thus, the different angle means different type of stairs. Firstly, there are several types of stairs: portable ladders, ship’s ladders, attics ladders, normal ladders, entrance ladders, driveways or wheel chair access. For all of these stair types, the angle varies form 70/90 degrees to 5 degrees. On the pictures below, you can see the generally used degrees for each type of stairs.
Angles for Different Types of Stairs
Check the link below for more details.