Calculate rise, going, and pitch for your stairs
Designing a staircase that is safe, comfortable, and compliant with UK Building Regulations requires careful calculation of the rise (the height of each step), the going (the depth of each tread), and the pitch angle. These three measurements are interdependent: the floor-to-floor height and the available horizontal run determine how many steps you need, which in turn sets the individual rise and going dimensions. UK Building Regulations Approved Document K sets clear limits for domestic staircases: the maximum individual rise is 220mm, the minimum going is 220mm, and the maximum pitch angle is 42 degrees. The 2R + G rule (twice the rise plus the going) should fall between 550mm and 700mm for a comfortable stride. Stairs that fall outside these parameters feel unsafe or tiring to use and will not pass Building Control inspection. This calculator takes your floor-to-floor height and available horizontal going length, then works out the optimal number of risers targeting an ideal rise of approximately 190mm. It calculates the exact rise and going per step, the pitch angle, the stringer length (the diagonal board that supports the treads), and checks compliance against UK Building Regulations. If any dimension falls outside the permitted range, the calculator flags it so you can adjust the available going length or consider a different staircase layout such as a quarter-turn or half-turn design.
To design your staircase dimensions: 1. Measure the floor-to-floor height in millimetres. This is the total vertical distance from the finished floor level of the lower storey to the finished floor level of the upper storey. Include the floor construction depth (floorboards, screed, tiles, etc.). 2. Measure the available going length in millimetres. This is the horizontal distance available for the staircase from the face of the first riser to the nosing of the landing above. The going length is constrained by the room layout. 3. Optionally adjust the staircase width. The minimum width for a domestic staircase under UK Building Regulations is 800mm between walls or 750mm between handrails. The default of 860mm is a common standard UK width. 4. Review the results. Check that the rise, going, and pitch angle are all within the UK Building Regulations limits shown. The 2R + G comfort check should be between 550mm and 700mm. 5. If any dimension is flagged as non-compliant, increase the available going length (which reduces the pitch) or consider a different staircase type.
The staircase calculation follows UK Building Regulations guidance: Start with the ideal rise of 190mm. Divide the floor-to-floor height by 190 and round to the nearest whole number to get the number of risers. For a height of 2,600mm: 2,600 / 190 = 13.68, rounded to 14 risers. The actual rise per step = floor-to-floor height / number of risers. For 14 risers: 2,600 / 14 = 185.7mm. The number of goings (treads) is always one less than the number of risers (because the landing counts as the final tread). Going per step = available going length / (risers - 1). For 4,000mm going with 14 risers: 4,000 / 13 = 307.7mm. Pitch angle = arctan(rise / going) converted to degrees. For 185.7 / 307.7: arctan(0.603) = 31.1 degrees. Stringer length = square root of (height squared + going length squared). For 2,600 and 4,000: sqrt(6,760,000 + 16,000,000) = sqrt(22,760,000) = 4,771mm. The 2R + G comfort check = (2 x 185.7) + 307.7 = 679mm. This is within the 550-700mm comfort range. UK Building Regulations compliance: rise 185.7mm (within 150-220mm, compliant), going 307.7mm (max 300mm, over limit), pitch 31.1 degrees (within max 42, compliant).
This calculator designs a straight-flight staircase. For quarter-turn, half-turn, or winder staircases, the going measurement changes at the turn points and requires more complex geometry. The minimum headroom above any point on the staircase is 2,000mm, measured vertically from the nosing of each tread to the ceiling or soffit above. If headroom is tight, consider a steeper pitch (up to the 42-degree maximum) or lower the opening in the floor above. All staircases in the UK require a continuous handrail on at least one side, and stairs wider than 1,000mm need handrails on both sides.