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Calculate stair rise, run, tread count, angle, and stringer length. Includes a basic dimensional screen; verify the full design against current local requirements.
Calculator inputs
Enter measured project values. Results update only when you choose Calculate.
Method
The 2021 IRC R311.7.5 sets residential limits including a 7-3/4-inch maximum riser, 10-inch minimum tread depth, and no more than 3/8-inch variation between risers in a flight. IBC 1011 applies different commercial limits. Code editions and local amendments vary, and the 2024 IRC renumbered these stair provisions, so verify the adopted local text rather than treating this calculator as approval.
Use this for basic rise-and-run layout. In the 2021 IRC, related provisions include headroom at R311.7.2 and landings at R311.7.6; width, nosing, handrails, guards, winders, finished-floor build-up, and local amendments remain outside this screen.
Top of finished upper floor down to top of finished lower floor — including any underlayment and flooring thickness on both ends. A 1/2-inch error here lands as a 1/2-inch error on the bottom riser, which fails inspection.
Most builders aim 7 to 7-1/2 inches residential. Divide total rise by 7.25 (or 7.0 commercial), round to the nearest whole number, then divide total rise back by that number for the actual riser height. Confirm the result against code maxima.
Tread count is one less than riser count on a straight flight (the upper floor acts as the top tread). Multiply tread depth (10 inches residential, 11 inches commercial as the floor) by tread count to get total run.
Stringer = sqrt(rise squared + run squared). Then review headroom, landing requirements, handrails, guards, nosing, width, variation, winders, and any local amendments under the code edition adopted for the project.
Total rise from finished floor to finished floor is typically 108 to 114 inches with framing thickness. Divide by 7.25 (residential target) to get 14.9 to 15.7 — round to 15 risers. Actual riser height is total rise divided by 15: usually 7.2 to 7.6 inches per riser.
The upper floor counts as the top tread. A 15-riser stair has 14 treads in the run (or 14 stringer cutouts above the bottom). On a stair landing in the middle, count separately above and below the landing.
The IRC generally governs one- and two-family residential work, while the IBC covers most commercial occupancies and can use different dimensional and safety provisions. Section numbers and requirements change by edition and local amendment, so identify the adopted code and occupancy before using any limit.
Yes — measure finished-to-finished. Building from rough framing elevations is the most common stair callback in remodel work because the bottom riser ends up too tall when the tile guy floats out his thinset and the top riser ends up too short under the new hardwood.
Separate plan workflow
This calculator solves one bounded formula from the inputs shown. BuildVision AI supports reviewed plan takeoff, complete-document CSV, and editable quote lines; the estimator owns pricing and final bid approval.