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Calculation Tool

Stair Calculator: Risers and Treads

Enter the floor-to-floor height to get the riser count, tread depth, Blondel value and pitch, checked against Turkish zoning limits and drawn as a section.

Stair details

Height from the finished floor of the lower storey to the finished floor of the upper storey, including floor finishes.

Result

Number of risers

19

Riser height

15.79 cm

Number of treads (excl. landing)
17
Tread depth
31.5 cm
Blondel (2r + b)
63.1 cm
Pitch angle
26.6°
Risers per flight
10 + 9
Horizontal run of treads
5.36 m
Approximate plan size
3.84 × 3.52 m
Half-landing depth
100 cm

The half-landing depth is taken as equal to the flight width.

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Regulation and ergonomics check

  • Riser ≤ 16 cm — Article 31/2-aCompliant
  • Tread ≥ 27 cm — Article 31/2-bCompliant
  • 2r + b = 60–64 cm — Article 31/2-bCompliant
  • Flight width ≥ 100 cm — Article 31/1-aCompliant
  • Pitch ≤ 40° — ergonomic guidelineCompliant
  • The dimensions are within the regulatory limits and the ergonomic range.

Source: Planned Areas Zoning Regulation (Planlı Alanlar İmar Yönetmeliği), Article 31.

Side view (section)

lower floorupper floorlanding26.6°br300 cm6.36 m
r = 15.79 cm · b = 31.5 cm · θ = 26.6° · H = 300 cmDrawn to scale. For a straight stair this is a true section; for L and U types the flights and the half landing are unfolded onto one plane.

The three dimensions of a comfortable stair

A stair's comfort comes not from a single dimension but from the ratio between riser, tread and pitch.

  • Riser: equal and within the limit

    The floor-to-floor height is divided into equal risers; even a single step of a different height breaks the rhythm and increases the risk of tripping. The regulation limits the riser to 16 cm in buildings without a lift and 18 cm in buildings with a lift.

  • Tread: in step with the stride

    Tread depth is chosen according to the human stride. The Blondel relation requires 2r + b to stay between 60 and 64 cm; the Planned Areas Zoning Regulation also adopts this formula and a 27 cm minimum.

  • Pitch and landing

    As the riser grows and the tread shrinks, the stair gets steeper. Splitting long flights with a half landing creates a resting point; L and U layouts fit the stair into a shorter footprint.

RISERS n = ⌈ FLOOR-TO-FLOOR HEIGHT ÷ TARGET RISER ⌉ · ACTUAL RISER r = FLOOR-TO-FLOOR HEIGHT ÷ n

TREAD b = 63 − 2r (BLONDEL) · AT LEAST 27 cm

HORIZONTAL RUN = (n − NUMBER OF FLIGHTS) × b · PITCH = arctan(r ÷ b)

Stair step dimensions by floor-to-floor height

Floor-to-floor heightRisersRiserTreadHorizontal run
260 cm1715.29 cm32.5 cm5.2 m
280 cm1815.56 cm32 cm5.44 m
300 cm1915.79 cm31.5 cm5.67 m
320 cm2016 cm31 cm5.89 m
350 cm2215.91 cm31 cm6.51 m

Values are calculated for a straight single-flight stair in a building without a lift (riser ≤ 16 cm), using the Blondel ideal of 63 cm. In a building with a lift the riser may go up to 18 cm, so the number of risers and the stair length decrease.

What does the Planned Areas Zoning Regulation say?

Stair dimensions in Turkey are governed by Article 31 of the Planned Areas Zoning Regulation (Planlı Alanlar İmar Yönetmeliği; Official Gazette of 3 July 2017, No. 30113). The provisions this tool relies on:

  • Riser height may not exceed 0.16 m in buildings without a lift and 0.18 m in buildings with a lift. (Article 31/2-a)
  • Tread depth is calculated with the formula 2a + b = 60–64 (a: height, b: depth) and may not be less than 0.27 m. (Article 31/2-b)
  • In balanced (winder) stairs, the tread may not be narrower than 0.10 m at the narrow end or 0.27 m at the middle of the tread. (Article 31/2-c)
  • Tread nosings must be flush, without projections. (Article 31/2-ç)
  • Common stair flights and landings must be at least 1.20 m wide in residential buildings and 1.50 m in other buildings; stairs inside a dwelling unit must be at least 1.00 m wide. (Article 31/1-a)
  • The requirements of paragraphs one and two do not apply to internal stairs leading to attic rooms connected to top-floor units. (Article 31/3)
  • Spaces under stairs with a height of less than 1.80 m are closed off. (Article 31/6)

For stairs inside a dwelling unit, the regulation separately sets only the flight width; the tread-dimension provision (31/2) is written without distinguishing between stair types. The tool therefore applies the same step limits to internal villa and duplex stairs. Practice may vary between authorities; consult the relevant municipality before preparing the permit project. The text was checked against the current version on mevzuat.gov.tr in September 2026.

How do you calculate the number of stair steps?

The floor-to-floor height (from the finished floor of the lower storey to the finished floor of the upper storey) is divided by the target riser height and rounded up to the next whole number; this is the number of risers. The floor-to-floor height is then divided by the number of risers to find the actual, equal riser. For example, a 300 cm floor-to-floor height with a 16 cm target gives 19 risers of about 15.8 cm each. In a straight single-flight stair there is one tread fewer than risers, because the last step lands on the upper floor.

What is the maximum riser height?

Under Article 31 of the Planned Areas Zoning Regulation, riser height may not exceed 0.16 m in buildings without a lift and 0.18 m in buildings with a lift. Internal stairs from a top-floor unit to the attic are exempt from this requirement. Ergonomically, risers of 15–18 cm are commonly considered comfortable; higher risers make the stair steeper.

What is the Blondel formula?

The Blondel relation ties step dimensions to the human stride: two riser heights plus one tread depth (2r + b) should be close to the average stride length. The Planned Areas Zoning Regulation requires this sum to stay between 60 and 64 cm and the tread to be no less than 27 cm. The tool calculates the tread with a 63 cm target; for example, a 16 cm riser gives a 31 cm tread.

What should the dimensions of an internal villa stair be?

In residential buildings, stairs inside a dwelling unit must be at least 1.00 m wide under the regulation. The regulation sets no separate step dimensions for internal stairs; applying the general provision of Article 31, a villa without a lift may have a riser of at most 16 cm and a tread of at least 27 cm. At a floor-to-floor height of 3.00 m this means 19 risers and a tread of about 31.5 cm. If the stair is the focal point of the space, keeping the flight wider than the minimum lets two people pass each other comfortably.

What should the pitch of a stair be?

The pitch follows from the ratio of riser to tread: angle = arctan(r ÷ b). In a stair that complies with the regulatory limits the angle is at most about 34° (18 cm riser, 27 cm tread). In residential stairs a range of 25–35° is common; stairs steeper than 40° are considered steep for daily use and increase the risk of falling on the way down.

When is a half landing needed?

The regulation sets no upper limit on the number of steps in a flight; however, in common stairs the landing, like the flight, must be at least 1.20 m wide in residential buildings. In design practice, not exceeding 18 risers per flight is a common recommendation: long flights are tiring and leave no resting point. In L and U stairs the half landing splits the flight in two and fits the stair into a shorter plan.

This tool is for preliminary sizing; it does not replace the architectural and structural project. Floor finish thicknesses, headroom below beams, winder steps, balustrades and fire escape requirements must be addressed separately in the project. The final word on interpreting the regulation belongs to the authority issuing the building permit.

Related services

Villa Design in AnkaraArchitectural Design in AnkaraSmart Villa ArchitectureInterior Architecture Studios in Ankara

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