Bespoke contemporary staircase by Continox — rise 195mm, going 250mm, 2R+G = 640mm. Sweet-spot comfort specification on premium domestic projects.

Where the Formula Comes From

The 2R + G formula was developed in the 17th century by François Blondel, a French architect and mathematician, who observed that comfortable staircase climbing maintained a consistent relationship between vertical rise and horizontal stride. Blondel noted that on level ground a person's average stride is approximately 600–650mm, but on stairs each unit of vertical rise consumes twice the energy of horizontal travel — so the effective stride needs to account for the rise twice. His formula, refined and adopted into modern design standards, has held up remarkably well across three centuries of staircase ergonomics research.

In the UK the formula sits within BS 5395-1 (Stairs — Code of practice for the design, measurement and construction of stairs and stepped pavements). It's not an absolute minimum the way Part K rise and going limits are — a flight slightly outside the 550–700mm range is still legal — but it's the recognised comfort target, and it's what an experienced staircase designer aims for on every project.

The reason it survives in modern design is that human gait dimensions haven't meaningfully changed since Blondel's time. The average UK adult stride length on level ground is still 650–710mm; the energy cost of vertical climbing relative to horizontal walking is still approximately 2:1; and the rise/going relationships that produce a comfortable climb haven't shifted. The formula remains the simplest accurate predictor of staircase comfort.

How to Apply the Formula

Three values are needed for any staircase calculation:

Floor-to-floor height (FFH). The vertical distance from the finished surface of the lower floor to the finished surface of the upper floor. Typical UK values: 2,400mm in older single-storey extensions, 2,600mm in most modern domestic builds, 2,700–3,000mm in higher-end residential and Victorian/Edwardian properties.

Number of risers. Calculated by dividing FFH by the target rise (typically 190–200mm). The number must be a whole number — fractional risers don't exist. A 2,700mm FFH at 200mm rise gives 13.5 risers, so the design uses either 13 risers at 207.7mm or 14 risers at 192.9mm.

Going. The horizontal depth of one tread, measured nosing to nosing. Set independently to suit the available footprint and the target 2R+G value.

The calculation runs in sequence: FFH ÷ chosen riser count = rise. Then 2R + G = comfort check. Adjust going to bring 2R + G into 550–700mm range.

Worked Examples — Real Project Numbers

Three real-world calculations covering the most common UK domestic scenarios. Each shows the FFH, the risers chosen, and the resulting 2R+G value with comfort assessment.

The Comfort Zone — Visualised

The 550–700mm comfort range can be visualised as a rise-versus-going chart with the comfort band highlighted. Any combination of rise and going inside the band passes the comfort check; combinations outside it fail.

What Happens Outside the Range

A flight outside the 550–700mm range is technically legal in most cases (as long as Part K rise and going limits are respected) but produces measurable user discomfort. The two failure modes are different in feel and consequence.

Below 550mm — the cramped flight

A flight where 2R+G drops below 550mm forces the user into a shortened stride on every step. On ascent this feels effortful and "stair-y" — the user is conscious of climbing stairs rather than moving naturally between floors. On descent the cramped going limits foot placement and increases trip risk, particularly for users carrying objects or wearing footwear with heel projection. The fix is almost always to lengthen the going (typically by 20–30mm) which brings 2R+G back into range without changing rise.

Above 700mm — the over-extended flight

A flight where 2R+G exceeds 700mm forces the user into an over-extended stride. On ascent this feels labouring — the rise is generous, the going is long, and each step covers too much horizontal distance for natural walking pace. On descent the long going can produce a "rocking" feel where the user's foot lands further forward than expected. The flight often photographs beautifully (long shallow stairs are visually elegant) but feels wrong in use. The fix is to shorten the going or increase the rise to bring 2R+G back into range.

2R + G — Reference Combinations

Common rise/going combinations with their 2R+G values and comfort assessment. Use as a quick lookup at the design stage.

Bespoke flight — R195/G250, 2R+G = 640mm

Floating flight — R197/G245, 2R+G = 639mm (Romsey)

2R + G Across Staircase Types

The 550–700mm comfort range is universal but the position within the range varies by staircase use. The five common scenarios below show where to target 2R+G for each project type.

Premium domestic — 620–650mm. Sweet-spot specification for bespoke floating, central spine, and feature staircases. Pitch under 40°, generous going, and rise around 190mm. This is the comfort zone Continox targets on every premium project. See our bespoke modern staircase range for the full specification.

Standard domestic — 600–660mm. Typical new-build and renovation. Pitch around 38–42°, going 220–250mm, rise 195–210mm. Compliant, comfortable, and efficient on footprint.

Loft conversion — 580–650mm. Compressed footprint forces the going into the lower end of the range and the rise toward the higher end. The flight feels steeper than a primary stair but remains compliant. Pitch up to 42° (the Part K maximum). For loft-specific guidance see our loft staircase regulations.

Public and commercial — 580–620mm. Higher rise/going ratio paired with longer going to accommodate fast simultaneous use during normal occupancy and emergency escape. Pitch under 38°, going typically 280–320mm, rise 170–185mm. The shallower pitch reduces fatigue on long descents. See our school staircase regulations for sector-specific specifications.

External and fire escape — 590–640mm. Designed for fast confident descent during evacuation. Pitch around 38°, going 250–280mm, rise 175–190mm. The geometry prioritises descent speed and landing predictability over ascent comfort. For full external specifications see our external staircase range.

Why Bespoke Staircases Hit the Sweet Spot

Stock and pre-fabricated staircases come with fixed rise and going values set by the manufacturer's standard production sizes. A typical off-the-shelf flight has a rise of 195–210mm paired with a going of 215–225mm — producing 2R+G values of 605–645mm. The flight is technically compliant and inside the comfort range, but the rise/going ratio is set to suit production economics rather than user comfort, and the result is usually a flight at the steeper end of the comfort zone.

On a bespoke staircase the rise and going are set independently to suit the floor-to-floor height, available footprint, and target pitch. A bespoke flight at 2,600mm FFH typically delivers 200mm rise paired with 240mm going — 2R+G = 640mm, sweet spot, comfortable to climb. The cost difference versus a stock flight is often less than expected because the bespoke design optimises material use against the actual project rather than rounding to standard sizes. See our bespoke staircase cost guide for detailed pricing.

For projects where the staircase is a feature element — open-plan layouts, double-height entrances, period properties — the bespoke advantage is amplified. The same FFH that produces a steep stock flight at 2R+G = 605mm can produce a generous bespoke flight at 2R+G = 645mm with no change in footprint, just by allocating the geometry differently.