Staircase Rise, Run & Railing Calculator
Calculate stair dimensions including rise, going, number of steps, total staircase length, and spindle spacing for any floor-to-floor height, compliant with UK Building Regulations.
Staircase Design Guide
UK Building Regulations Part K
Approved Document K sets stair dimensions. Private stairs (domestic): rise maximum 220mm. Going minimum 220mm. Pitch maximum 42°. The '2R + G = 550-700mm' formula: twice the rise plus the going should be 550-700mm (ergonomic comfort zone). Loft conversion stairs: allowed up to 42° pitch and 220mm rise, but going can be as low as 145mm for alternating tread stairs. Public/commercial: rise maximum 180mm. Going minimum 280mm. Open risers: if open, the gap must prevent a 100mm sphere passing through
Calculating Stair Dimensions
Number of risers = floor height / target rise. Round to nearest whole number. Actual rise = floor height / number of risers. Example: 2600mm floor height. Target rise 175mm. 2600/175 = 14.86 → round to 15 risers. Actual rise = 2600/15 = 173.3mm. Using 2R+G formula: G = 600 − 2×173.3 = 253mm going. Total run = going × (number of risers − 1) = 253 × 14 = 3,542mm horizontal floor space. Note: number of treads = number of risers − 1 (the top landing counts as a tread, not a separate step).
Handrails and Balustrading
Handrail height (domestic): 900mm minimum from pitch line (surface of tread nosings) to top of handrail. Baluster spacing: maximum 100mm gap — a 100mm diameter sphere must not be able to pass through (child safety). Handrail required: on any staircase with a total rise exceeding 600mm. Both sides: on stairs wider than 1000mm. Newel post positioning: at the start, end, and any change of direction. Timber stair regulations: notching structural timber for staircases is strictly limited — consult a
Common Staircase Mistakes
Inconsistent rises: if any single step is different from the others, it is a significant trip hazard. All rises must be the same within 5mm tolerance. Wrong starting point: the measurement of floor-to-floor height must be exact — measure between finished floor levels, not subfloor. Ignoring headroom: calculate headroom from the pitch line, not just the height at the bottom. Low ceilings eat headroom rapidly as the stairs ascend toward a landing. Undersize going: a short going feels steep and uns
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