Staircase Calculator — UK Building Regs Part K Compliance

This calculator determines the optimal staircase geometry based on your total rise (floor-to-floor height) and available going (horizontal run). It checks all results against UK Building Regulations Approved Document K.

Formulas used

• Number of risers = Total Rise / Target Riser Height (rounded to nearest whole number)
• Actual riser height = Total Rise / Number of Risers
• Going depth = Available Going / (Number of Risers - 1)
• Pitch angle = arctan(Riser Height / Going Depth)
• Stringer length = √(Total Rise² + Available Going²)

Part K compliance checks

• Maximum riser: 220mm for private stairs (minimum 150mm)
• Going: 220–300mm for private stairs (Table 1.1)
• Maximum pitch: 42° for private stairs
• Minimum headroom: 2000mm measured vertically above the pitch line
• 2R + G rule: Twice the riser plus the going should be 550–700mm (Table 1.1 note)

Note: Part K sets no general minimum widthfor a private stair. The only width figure in Approved Document K is the 900mm minimum in para 1.16, which applies only to a flight in the entrance storey where an unavoidable stepped change of level occurs on a severely sloping plot. (For comparison, Part M stepped-access dwellings use 850mm, measured 450mm above the pitch line.) There is also no “rise × going” product limit in Part K.

Standards

All checks reference Approved Document K (2013 edition) for private domestic stairways. Table 1.1 has two other rows with tighter limits: utility stairs and general access stairs, the latter covering common stairs in flats. There is no separate institutional or assembly row in the 2013 edition. All risers must be equal in height and all goings must be equal in depth.