Stair Calculator
How to Use This Calculator
- Select your stair type (private, institutional, or commercial) to apply correct UK Building Regulations
- Enter the total rise – the vertical distance from the lower floor level to the upper floor level
- Choose your calculation mode based on what you know about your staircase
- The calculator will determine the optimal number of steps, individual rise, going, and pitch angle
- Review the compliance status to verify your stairs meet UK regulations
UK Building Regulations for Stairs
Staircases in the UK must comply with Approved Document K of the Building Regulations. The requirements vary depending on the stair type and location.
| Stair Type | Min Rise (mm) | Max Rise (mm) | Min Going (mm) | Max Going (mm) | Max Pitch |
|---|---|---|---|---|---|
| Private / Domestic | 150 | 220 | 220 | 300 | 42° |
| Institutional / Assembly | 150 | 190 | 250 | 400 | 38° |
| Other (Commercial) | 150 | 190 | 250 | 400 | 38° |
Key Staircase Formulae
The 2R + G Rule: 2 × Rise + Going = 550mm to 700mm
This formula creates comfortable and safe stairs that match natural walking rhythm.
Pitch Angle: tan(pitch) = Total Rise ÷ Total Run
The pitch determines how steep your staircase will be. Lower angles are easier to climb but require more space.
Number of Risers: Total Rise ÷ Individual Rise
Always round to the nearest whole number. The number of treads is typically one less than the number of risers.
Staircase Terminology
- Rise: The vertical height from one tread surface to the next. This is measured between the tops of consecutive treads, not the physical height of the riser board.
- Going (Tread): The horizontal depth of each step, measured from the nosing of one step to the nosing of the next. Minimum 220mm for domestic stairs.
- Total Rise: The complete vertical distance between two floor levels that the staircase must span.
- Total Run (Total Going): The total horizontal distance covered by the staircase from bottom to top.
- Pitch: The angle of the staircase measured from horizontal. Steeper stairs have higher pitch angles.
- Nosing: The front edge of a tread that projects beyond the riser. Typically 15-25mm for added foot space.
- String (Stringer): The structural members running along each side of the staircase that support the treads and risers.
- Headroom: The vertical clearance from the nosing line to any overhead obstruction. Minimum 2000mm required in the UK.
Design Considerations
- Consistency: All rises and all goings in a flight of stairs must be identical. Variations cause trips and falls.
- Landings: Domestic staircases should not exceed 36 steps without an intermediate landing. Landings should be at least as wide as the staircase.
- Handrails: Required on at least one side for domestic stairs narrower than 1000mm, and on both sides if wider. Height should be 900-1000mm above the pitch line.
- Width: Minimum 800mm for private stairs, 1000mm for stairs serving more than one dwelling, and 1100mm for institutional buildings.
- Headroom Clearance: Maintain at least 2000mm vertical clearance throughout the staircase and on landings.
- Winders: Tapered treads are permitted but have specific minimum going requirements measured at the centre line and 270mm from the inner edge.
Common Design Scenarios
Standard Domestic Staircase
For a typical two-storey house with a floor-to-floor height of 2700mm, you would need approximately 13-15 risers, each around 180-208mm high. With a going of 240-260mm, the total run would be 2880-3640mm. This creates a comfortable pitch of approximately 37-40°.
Space-Saving Stairs
When space is limited, use the maximum permitted rise (220mm for domestic) and minimum going (220mm). For a 2700mm total rise, this requires 13 steps with a going of 220mm, resulting in a total run of 2640mm and a steeper pitch of 42°.
Comfortable Low-Pitch Stairs
For easier climbing, especially for elderly users, aim for a rise of 150-170mm and a going of 260-280mm. This creates a gentler pitch of 30-35° but requires more horizontal space. For 2700mm total rise at 170mm per step, you need 16 steps.
Commercial or Public Building Stairs
These require more generous dimensions: maximum rise of 190mm and minimum going of 250mm. The increased going provides better footing in high-traffic areas. A 2700mm rise requires 15 steps at 180mm each, with goings of 250-280mm.
Frequently Asked Questions
What is the ideal staircase pitch angle?
The optimal pitch is typically between 37-40° for domestic stairs. This provides a good balance between comfort and space efficiency. The absolute maximum for private stairs is 42°, whilst commercial stairs typically should not exceed 38°.
How many steps can a staircase have without a landing?
A maximum of 36 steps (risers) is permitted in a single flight for domestic stairs. For institutional or assembly buildings, this is reduced to 16 steps. Landings provide rest points and improve safety.
Can all steps have different dimensions?
No. All risers in a flight must have the same height, and all goings must have the same depth. Inconsistent dimensions are a major cause of accidents as people expect uniform steps.
What if my calculations show non-compliant dimensions?
If your stairs don’t meet regulations, you have several options: adjust the total rise by modifying floor levels, change the number of steps, increase the horizontal space available for the staircase, or consider alternative stair configurations such as winders or a quarter-turn design.
Do I need Building Control approval for new stairs?
Yes, in most cases. Installing or altering staircases typically requires Building Regulations approval. Contact your local Building Control department before starting work. Replacement stairs that match existing dimensions may have simpler approval processes.
What is the minimum width for a domestic staircase?
The minimum width is 800mm for private stairs serving one dwelling. For stairs serving multiple dwellings or commercial premises, the minimum increases to 1000mm or 1100mm depending on the building type and occupancy.
How do I measure total rise accurately?
Measure from the finished floor level of the lower storey to the finished floor level of the upper storey. This includes all floor finishes such as carpet, laminate, or tiles. It’s not the structural floor height but the actual walking surface height.
What about open-plan living spaces with mezzanines?
Mezzanine stairs follow the same regulations as standard stairs. However, if the floor area served is very small (like a sleeping platform), alternative steep stair or ladder solutions might be acceptable. Always confirm with Building Control.
Measurement Tips
- Always measure from finished floor to finished floor, including all flooring materials
- Check measurements at multiple points as floors may not be perfectly level
- Consider ceiling height and ensure 2000mm minimum headroom throughout
- Account for door swings at top and bottom of stairs – doors must open onto landings, not over steps
- Verify your total run measurement includes sufficient space for any bottom nosing projection
- For replacement stairs, measure existing stairs carefully but don’t assume they’re compliant with current regulations
Safety Requirements
- Guarding required where there is a drop of more than 600mm – minimum height 900mm for domestic, 1100mm for other buildings
- Gaps in balusters or spindles must not permit a 100mm sphere to pass through
- Stairs should be adequately lit with switches at top and bottom
- Slip resistance is crucial – ensure appropriate tread materials, especially for external stairs
- Visual contrast at the leading edge of each step helps those with impaired vision
- Structural strength must support imposed loads – typically 1.5 kN/m² for domestic, higher for commercial
References
HM Government. (2013). The Building Regulations 2010: Approved Document K – Protection from falling, collision and impact. NBS. Available at: assets.publishing.service.gov.uk/media/60d5bdcde90e07716f516cfd/Approved_Document_K.pdf
Planning Portal. (2024). Building Regulations: Approved Documents. Ministry of Housing, Communities & Local Government. Available at: planningportal.co.uk
LABC. (2017). Approved Document K: Protection from falling, collision and impact – Technical Guidance. Local Authority Building Control. Available at: labc.co.uk