{"id":"stair-calculator","name":"Stair Calculator","shortName":"Stair Layout","canonicalUrl":"https://calcurhome.com/calculators/stair-calculator","catalogUrl":"https://calcurhome.com/api/calculators","category":{"id":"measurement-framing","name":"Measurement & framing","url":"https://calcurhome.com/calculators/category/measurement-framing"},"language":"en-US","audience":"US homeowners, DIYers and home-project planners","primaryKeyword":"stair calculator","secondaryKeywords":["stair rise and run calculator","stairs calculator","stair rise calculator","step calculator","riser height calculator","stair stringer length"],"description":"Plan straight stairs from total rise, maximum riser, tread depth, and width; calculate risers, treads, total run, slope, and stringer span.","directAnswer":"Divide total rise by the maximum permitted riser height and round up to a whole riser count. Divide rise again for equal actual risers. A typical floor-to-floor flight has one fewer tread than risers. Verify geometry, landings, headroom, guards, handrails, and code locally.","inputs":[{"key":"totalRise","label":"Finished floor-to-floor rise","unit":"in","defaultValue":108,"min":1,"step":0.125},{"key":"maxRiser","label":"Maximum riser height","unit":"in","defaultValue":7.75,"min":1,"step":0.125},{"key":"treadDepth","label":"Tread run","unit":"in","defaultValue":10,"min":1,"step":0.125},{"key":"stairWidth","label":"Stair width","unit":"in","defaultValue":36,"min":1,"step":0.5}],"formula":{"title":"Equal stair risers and straight-flight run","expression":"Risers = round up(total rise ÷ maximum riser); actual riser = total rise ÷ risers; treads = risers − 1; total run = treads × tread run; slope span = √(total rise² + total run²)","explanation":"Rounding the initial quotient up keeps equal risers at or below the entered maximum. The floor-to-floor model uses one fewer tread than risers and multiplies treads by selected run."},"measurementGuide":["Measure total rise vertically from lower finished floor to upper finished floor.","Include final flooring thicknesses because small changes affect riser uniformity.","Measure available horizontal space to finished obstructions and required landings.","Field-check headroom, width, nosing, handrail, guard, door, and landing conditions."],"buyingTips":["Obtain local code requirements and permits before final layout or material cutting.","Use graded structural lumber or an approved stair system sized for the design and span.","Plan connectors, blocking, landings, guards, handrails, finishes, and lighting together.","Build from one verified layout so every finished riser remains within permitted variation."],"workedExample":{"title":"Nine-foot floor-to-floor stair","scenario":"Total rise is 108 inches, maximum riser is 7.75 inches, and tread run is 10 inches.","result":"108 ÷ 7.75 rounds up to 14 risers at 7.714 inches; 13 treads create a 130-inch run."},"commonQuestions":[{"question":"How many steps do I need for a 9-foot rise?","answer":"A 108-inch rise divided by a 7.75-inch maximum requires 14 equal risers, each about 7.714 inches. In a typical floor-to-floor flight that produces 13 treads, but landing and local-code conditions can change the layout."},{"question":"Why are there fewer treads than risers?","answer":"In a floor-to-floor flight, the upper finished floor serves as the surface reached by the final riser, so a separate tread is not added there. Exterior steps or flights ending differently may need another interpretation."},{"question":"What is the maximum stair riser height?","answer":"Requirements depend on adopted code, occupancy, stair type, and jurisdiction. The 7.75-inch default is a common residential model-code value, not universal permission. Confirm the locally adopted edition, amendments, and project conditions before laying out stairs."},{"question":"Can I use the calculated slope span as stringer length?","answer":"Use it only as a geometric reference. A cut stringer needs extra material for end cuts and must satisfy structural depth, bearing, attachment, species, grade, and span requirements. Have the final stringer design checked professionally."}],"sources":[{"name":"International Code Council — 2024 International Residential Code","url":"https://codes.iccsafe.org/content/IRC2024P1","note":"Primary model-code source for residential foundations, reinforcement, masonry, and stair safety requirements."}],"defaultCalculation":{"inputs":{"totalRise":108,"maxRiser":7.75,"treadDepth":10,"stairWidth":36},"result":{"value":"14","unit":"risers","label":"Equal riser count","lines":[{"label":"Finished floor-to-floor rise","value":"108 in"},{"label":"Actual riser height","value":"7.714 in"},{"label":"Tread count","value":"13"},{"label":"Entered tread run","value":"10 in"},{"label":"Total horizontal run","value":"130 in"},{"label":"Straight slope span","value":"169 in at 39.7°"},{"label":"Approximate tread surface","value":"32.5 sq ft"}],"summary":"14 equal risers are 7.714 inches high, with 13 treads in this floor-to-floor model.","note":"Preliminary geometry only. Do not cut stringers from slope span; real stringers require material, bearing, landing, nosing, connection, and code details."}},"reviewedOn":"2026-08-03","disclaimer":"Planning estimate only. Verify product coverage, supplier rounding, local codes and structural requirements before purchase or construction."}