The angle that a stair takes to the horizontal is the stair angle. It is also called the pitch of a stair here we brought Why there are Stair Angles for Different Uses? Stair Critical Angle is the one angle of a stair, above which a stair is deemed to be unsafe. It should be around 50 degrees. The image bellow provides clear view of a range of methods used to climb up and down by foot from one level to another.