What is the ideal tread to riser ratio for stairs?

The ideal tread to riser ratio for stairs refers to the relationship between the depth of the tread (the horizontal part of the step) and the height of the riser (the vertical part of the step). The generally accepted standard for stair design recommends a combined measurement, often expressed in inches, that optimizes user comfort and safety.

The correct choice of 24-26 inches represents the ideal range where the sum of the tread depth and twice the riser height results in a comfortable and safe stair configuration. This ratio facilitates easier navigation and helps prevent accidents caused by missteps. A well-designed stair should allow for a natural and efficient movement pattern, accommodating various user needs, including those with mobility challenges.

In contrast, the other options fall outside the recommended range. The lower ranges, such as 15-18 inches, may be too steep or shallow, while the upper ranges, like 30-32 inches, might lead to excessively shallow treads or overly tall risers, which can create safety hazards. The goal of adhering to an ideal tread to riser ratio is to ensure that the stairs are both functional and comfortable for all users.