Stair Steps and Height Calculator

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The riser height (step height] at which an adult feels most comfortable is between 170 and 180 mm, and the tread depth is between 260 and 280 mm.
The height of all steps must be consistent within a 5mm margin of error. If the heights are irregular, there is a very high risk of tripping and falling.
When designing stairs, you must ensure a headroom of at least 2 meters so that your head does not hit the ceiling when coming down as well as when going up.
Applying the Blondel formula for walking comfort (2 x riser height + tread depth = 600~640mm] creates stairs with the most natural stride length.
If the number of steps of a straight staircase exceeds 15 or the height exceeds 3m, a 'landing,' a flat space for resting in the middle, must be provided for safety.

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Stair Design Calculator, Design Guide for Risers, Treads, and Comfortable Angles

Stairs are one of the most accident-prone areas in buildings. Even a height error of just 5mm can cause us to trip and fall because our brains fail to recognize it. If you input the building's floor height (total height] and desired step height, this calculator automatically designs the optimal number of steps and precise riser height by applying Blondel's Law, which determines the most comfortable position for ascending and descending.

Stair Quantity and Height Calculation Formula

The key to stair design is calculated based on even division and walking rhythm.

Total number of steps

Number of steps = Round up(Total height ÷ Desired riser height]

Confirmed Challenger Level

Actual height = Total height ÷ Number of steps

The total height is divided again by a fixed number of steps and adjusted so that all stair steps are identical without any error of 1mm.

Detailed Guide to Calculator Input Items

For accurate design, please check the dimensions of the finished surface at the site in millimeters.

1. General

This is the vertical height from the floor finish of the lower level to the floor finish of the upper level. It is accurate to measure based on the height of the final finishing material, such as tiles or flooring, rather than the concrete slab.

2. One step height, riser

This is the desired height of a single step. For homes or indoors, 170mm to 180mm is most comfortable, while for public facilities considering the elderly, it is set to 150mm to 160mm.

3. Step depth, step plate

This refers to the depth of the footplate. Considering adult foot sizes, a minimum of 260mm must be secured for safety, and typically, 280mm to 300mm is recommended.

Recommended Stair Dimensions by Use

use	Riser height (R]	Step depth (T]	note
Public institutions / schools	150 ~ 160mm	300mm 이상	Gentle and spacious area (㎡] correspondence
Standard house (standard]	170 ~ 180mm	280 ~ 300mm	A balance of space efficiency and comfort
Small house / Attic	190 ~ 210mm	240 ~ 260mm	Applicable in confined spaces

Expert Know-how and Checklists

This is a key design point for safe and comfortable stairs.

Uniformity of all step heights
This is the first principle of stair construction. If steps of different heights are mixed in the middle, our brains cannot perceive them, and we are 100% guaranteed to fall. All steps must be identical without a 1mm margin of error.
Installation of stair landing
If the height exceeds 3m or the number of steps is 15 or more, a landing must be installed as a flat space to rest in the middle. It is generally safe to secure a space of approximately 1.2㎡ in width.
Secure headroom
Make sure to check that the vertical distance from the tip of the stair to the ceiling is at least 2,000mm to 2,100mm so that you do not hit your head while climbing the stairs.

Frequently Asked Questions (FAQ]

Q. Why are stair nosings made?
A. By protruding the ends of the treads by about 20mm to 30mm, the effective surface area for stepping is widened, and the end of the stairs is visually recognized, which helps prevent misstepping accidents.

Q. How about stairs with only treads and no risers (open risers]?
A. While the sense of openness provides excellent interior design appeal, there is a risk of feet getting caught in the gaps. For safety, if you have children, the gaps between the risers must be installed narrowly, at 100mm or less.

Q. What should be considered when designing a spiral staircase?
A. Since the spiral narrows as it approaches the central axis, it must be designed so that the depth of the step plate at a point 30cm away from the center, where people mainly step, is at least 260mm.