Staircase Rise & Going Calculator

Staircase Design Guide (UK Building Regs Part K)

What do I need to know about Key Terms and Limits?

Staircase terminology: rise — the vertical height of each step. Going — the horizontal depth of each tread (front to back of usable step). Pitch — the angle of the staircase from horizontal. Total rise — floor-to-floor vertical height. UK Building Regulations Part K limits (private domestic stairs): maximum rise: 220mm per step. Minimum going: 220mm per step. Maximum pitch: 42°. Maximum 16 risers in a single flight (without a landing). Minimum headroom: 2000mm (2m) measured vertically. The relationship between rise and going is what determines whether a staircase feels comfortable and safe to use, rather than either measurement alone.

What do I need to know about The 2R + G Rule?

The most important comfort formula: 2 × Rise + Going should be between 550mm and 700mm. Ideal target: around 600-620mm. Why: this relates the step proportions to the natural human stride. Stairs that satisfy this rule feel comfortable to climb. Stairs that violate it feel awkward — either cramped (too little going) or stretched (too much going for the rise). Examples: rise 190mm, going 230mm: 2(190) + 230 = 610mm ✅ comfortable. Rise 220mm, going 220mm: 2(220) + 220 = 660mm — within the acceptable range, but steeper and less comfortable than a staircase closer to the lower end of the range.

What's the key thing to understand about Calculating Step Count?

Process: 1. Divide total rise by preferred individual rise to get number of risers. Total rise 2600mm ÷ 190mm = 13.7. Round to nearest whole number: 14 risers. 2. Recalculate exact rise: 2600 ÷ 14 = 185.7mm per riser. 3. Number of treads (goings) = risers minus 1 (the top step is the landing). 14 risers = 13 goings. 4. Going = available horizontal run ÷ number of goings. 3500mm ÷ 13 = 269mm per going. 5. Check 2R + G: 2(185.7) + 269 = 640mm — within range, comfortable. 6. Check pitch: arctan(rise/going) to confirm the resulting angle stays within the maximum 42° allowed under Part K.

What should I know about Other Requirements?

Headroom: minimum 2000mm vertical clearance above the pitch line. For loft conversions, often the tightest constraint. Reduced headroom (1900mm at edge) sometimes permitted for loft conversions under specific rules. Handrails: required on at least one side if stairs wider than 1000mm; both sides if wider than 1000mm. Handrail height: 900-1000mm above pitch line. Width: no minimum width in Part K for private stairs, but practically 600mm+ (800mm+ comfortable). Common stairs in flats: minimum 1000mm width, reflecting the higher traffic and shared-use nature of communal staircases compared to a private house.

What should I know about Why 2R+G Must Fall Between 550 and 700mm?

The 2R+G rule (twice the rise plus the going, which should total between 550mm and 700mm, ideally close to 600mm) exists because it approximates a comfortable, safe stride length for ascending and descending stairs — it's based on long-observed ergonomics of how people naturally walk on stairs, balancing how far forward (going) and how far up (rise) each step moves a person per stride. A staircase with a low 2R+G value (steep rise, short going) forces an unnaturally cramped stride, increasing trip risk, while a high 2R+G (shallow rise, long going) forces an unnaturally long stride, which is tiring and can feel unstable, particularly descending. This single formula is why stair designs can't simply minimise the rise for comfort or maximise the going for safety independently — the two dimensions are deliberately constrained together.

What do I need to know about Consistency Requirements Across a Flight?

Beyond meeting the correct rise and going ranges, Part K requires every step within a single flight to have the SAME rise and the SAME going, with only very small manufacturing tolerances allowed (typically ±5mm maximum variation between the largest and smallest within a flight for rise, and similar tight tolerance for going). Inconsistent steps are a genuine, well-documented trip hazard — the human gait adapts to a repeated rhythm after the first couple of steps, and an unexpected variation partway up or down a flight (even a few millimetres different) is a common cause of stumbles, because the foot is placed based on the rhythm established by preceding steps rather than being consciously checked each time. This consistency requirement is why staircase design calculations always divide a fixed total rise by a whole number of equal steps, rather than allowing a flight to taper or vary to fit an awkward space.

What should I know about Pitch Angle Limits for Private Stairs?

UK Building Regulations don't just set rise and going limits individually — they also cap the overall pitch (steepness) of a private stairway, which is the angle the stair makes with the horizontal. Approved Document K sets a maximum pitch of 42° for a standard private staircase, meaning even if individual rise and going figures technically satisfy the 2R+G rule, the resulting angle must still be checked separately. A stair with a 220mm rise and 220mm going, for example, produces a 45° pitch, exceeding the limit even though other rules might appear satisfied, so pitch should always be checked as a final verification once rise and going are chosen. Steeper pitches (up to 56°) are only permitted for alternating tread/space-saver stairs used for loft conversion access under specific conditions, not for a normal flight serving multiple rooms. A shallower pitch, generally more comfortable and safer, is always achievable by increasing the going relative to the rise, which is why wider stairwells that allow a longer going are preferable wherever floor space permits. Pitch is calculated as the arctangent of rise divided by going, and most stair calculators will flag this automatically alongside the 2R+G check.

Worked Example: Rise and Going for a 2,600mm Floor-to-Floor Height

For a floor-to-floor height of 2,600mm, aiming for a rise close to the comfortable 170-190mm range used in most private UK staircases: trying 13 risers gives 2,600 ÷ 13 ≈ 200mm — slightly over the usual comfortable maximum. Trying 14 risers gives 2,600 ÷ 14 ≈ 185.7mm — comfortably within range and giving 13 goings (one fewer going than risers, since the top floor level itself is not a going). Checking the 2R+G rule with a chosen going of 250mm: 2(185.7) + 250 = 371.4 + 250 = 621.4mm, which falls within the required 550-700mm range, confirming this is a workable, compliant combination. Checking pitch angle: arctan(185.7 ÷ 250) ≈ 36.6°, within the maximum 42° allowed for a private stair under Approved Document K. This is exactly the iterative process — pick a riser count, check the resulting rise, check 2R+G, check pitch — that a stair calculator automates, because the first riser count tried rarely satisfies all three checks simultaneously.

What Headroom Clearance Do Building Regulations Require?

Beyond rise, going, and pitch, Approved Document K (England) requires a minimum headroom of 2.0m, measured vertically from the pitch line (an imaginary line drawn along the nosings of the treads) up to any ceiling, beam, or structure above — including loft hatches, sloping ceilings under a roof, and landing floor edges. This clearance must be maintained across the full width of the stair, not just down the centre line, which commonly catches people out designing a loft stair squeezed under a sloping roof: the headroom at the side of the stair (where the roof slope is lower) can fail even if the centre of the stair has ample clearance. Where full headroom genuinely can't be achieved (common in loft conversions), Building Regulations allow a slightly reduced headroom of 1.9m at the centre line reducing to 1.8m at the side of the stair, but only as a specific loft-conversion relaxation, not as a general rule for ordinary stairs.

How Do Winders and Landings Change the Going Calculation?

A winder is a tapered tread used to turn a staircase around a corner without a full landing — common where space is tight. Because a winder tread is wider on its outer edge than its inner edge, its 'going' is measured at a specific point: 270mm in from the narrow (inner) edge of the tread, which is roughly where a typical foot would fall when walking around the turn — not at the tread's centreline and not at its widest point. This measured-going-point rule exists specifically so winders are held to the same minimum going requirement as straight treads, despite their tapered shape. A landing, by contrast, is simply a flat platform interrupting a flight (required at least every 16 risers maximum for certain stair types, and always required at a change of direction beyond a certain angle) — a landing's own depth must be at least as great as the stair's width, and the rise/going rules don't apply to the landing itself since it's a flat floor section rather than a stepped one.