Per ADA, stairways must have uniform risers no higher than 7 inches and treads at least 11 inches deep, with slightly rounded or beveled nosings that project no more than 1.5 inches and have visual contrast. Treads must be slip-resistant, and all risers and treads within a flight must be consistent in height and depth.
Additional Information: https://www.ada.gov/law-and-regs/design-standards/standards-guidance/#top