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The ideal riser height for residential stairs typically falls between 6 and 7.75 inches (15-20 cm). Most building codes specify a maximum riser height (often 7.75 inches) but don't specify a minimum. However, very low risers can make stairs feel awkward to climb. Our calculator helps you find the optimal riser height for your specific total rise while maintaining the important 2R + T ratio between 24-25 inches.

The calculator divides your total rise by your desired riser height (if provided) or by a starting value of 7 inches (a comfortable middle ground). It then rounds this number to the nearest whole number (since you can't have a fraction of a step) and recalculates the actual riser height by dividing the total rise by this whole number. This ensures all risers are equal in height, which is crucial for safety and comfort.

Our calculator is based on common international building code requirements, but local regulations can vary. If you receive a warning about code compliance, try adjusting your desired riser height or tread depth. If you can't find a compliant solution within the tool, you may need to reconsider your staircase's location or design (like adding a landing for longer runs). Always verify final dimensions with your local building authority before construction.

This calculator is primarily designed for straight-run staircases. While it can provide basic dimensional calculations for spiral or curved stairs (like riser height), these stair types have additional requirements regarding tread shape, minimum width at certain points, and rotation angles that our current tool doesn't address. We recommend consulting with an architect or structural engineer for complex stair designs.

The 2R + T ratio (where R is riser height and T is tread depth) represents the relationship between step height and depth that matches the average human stride. When this sum falls between 24-25 inches (61-63.5 cm), stairs feel natural to climb. Values significantly outside this range can cause discomfort, increase tripping hazards, and feel awkward to use. This ratio has been established through ergonomic research and is incorporated into most building codes worldwide.

If you're planning to install floor coverings (like hardwood, tile, or carpet) after stair construction, you should account for their thickness in your total rise measurement. For example, if you're adding 0.5 inches of flooring material to both the upper and lower floors, your total rise would effectively decrease by 1 inch (2 × 0.5 inches). It's best to measure the actual floor-to-floor height after all floor coverings are installed for the most accurate calculations.

While our calculator focuses on riser and tread dimensions, stair width is another important consideration. Most residential building codes require a minimum width of 36 inches (91.5 cm) between handrails. However, 42-48 inches (107-122 cm) is more comfortable, especially for moving furniture or when two people need to pass. Always check local codes as some jurisdictions may have different requirements, particularly for egress stairs.

Our current calculator is designed for straight-run stairs without landings. If your design requires a landing (typically needed when a stair has more than 12-16 risers or changes direction), you would need to calculate each flight separately. The landing would count as a tread in the total run calculation. We're working on adding landing functionality to future versions of the tool.

Currently, our calculator doesn't have a save function, but you can easily take a screenshot of your results or write down the dimensions. For professional users who need to save multiple designs, we recommend creating a free account (coming soon) which will allow you to save, name, and organize your stair designs for future reference and easy sharing with clients or contractors.

While the calculator can provide basic dimensional calculations for commercial stairs, public buildings often have additional requirements regarding handrail design, landing sizes, tread nosing specifications, and accessibility compliance (like ADA requirements in the US). For commercial projects, we recommend using this tool for preliminary planning but consulting the specific codes for your building type and location before finalizing designs.