3D Stair Calculator — Staircase Design Tool
Try to design a staircase with our stair calculator and the simple guide that we provide for FREE. These tools assist in calculating stringer and spiral stairs dimensions and more various parameters. As a result, you get a set of stair plans, staircase 3D models and a list of materials to do it yourself.
This calculator helps you find:
- rise, run
- tread length, depth
- number of steps
- angle (slope)
- stringer length
- stringer minimum throat depth
- total run
KALK.PRO stair calculator is one of the most effective stair design services/softwares worldwide, and it's not just words! Automatically calculates, draws plans and 3D models, and outputs a cut list and PDF/PNG/OBJ files so you can continue creating your designs in other programs. As well:
Everything functionality of the design tools is available FULLY FREE OF CHARGE. There is no demo or trial period — paid only for downloads and premium drawings!
How to Calculate Stairs?
Building a staircase requires proper design, precise measurements and accurate calculations of a staircase so that it is safe and at the same time comfortable and practical.
To build the perfect stairs for a private dwelling, use our project, as well as the building codes currently in force in your country, region or state (local building-code requirements). With the stairs calculators you can determine all important staircase dimensions — simply and quickly.
In order to make your work with our stair project comfortable, we will give you the basic terms and definitions used in the calculation and staircase construction.
Types of staircase
When it comes to the stairs design, before choosing from the types of stairs design for your house you should consider some things — your budget, the available space for a staircase and types of material you'll be using.
Please remember: low quality building materials can be responsible for staircase collapse (contains wood imperfection — knots, cracks, checks and voids)
There are different kinds of stairs, classified by:
- shape: straight flight staircases, stairs with a turn, continuous stairs, mixed stairs;
- material: wooden staircase, metal, concrete, marble, etc.;
- slope: ramp (0-15°), stairs (20-45°), ladders (more than 50°);
- type of stair tread support : stringer stairs, floating stairs (mono stringer, cantilevered stair, suspended staircase).
Turning stairs are subclassified into:
- Quarter landing stairs (L-shaped, 90-degree turn);
- Half landing stairs, switchback (U-shaped, 180-degree turn);
- Quarter turn winder staircase (L-shaped, 90-degree turn);
- Half turn winder staircase or double winder staircase (U-shaped, 180-degree turn);
- Z-shaped stairs.
Continuous stairs are divided into three categories:
- circular stairs;
- spiral stairs;
- helical stairs.
Stairs can also be categorized according to the main types of tread support:
- stringer stairs — mono stringer, double stringer or even three stringers; open stringer (sawtooth) or closed stringer (housed or routed);
- cantilever staircase, suspended (treads are fixed only at one end);
- bolted staircases.
Stair terminology, stair parts
Before designing your staircase, you need to know the main elements of the stairs and dimensions needed to be measured for the stairs calculation (manually or with our calculator). Main parts and components of a staircase are:
- Stair Treads – the horizontal surface of a stair step.
- Rise – step height, the vertical distance between the top surfaces of adjacent treads.
- Going (Run) – the horizontal distance between two vertical projections of successive nosings.
- Tread Depth – Going or the tread run including the nosing projection (Pay attention, in Building codes “Tread Depth” is often used in meaning of Going, do not confuse these terms).
- Step – the combination of a tread and riser.
- Stair Riser – the vertical part of a step, forming the space between steps.
- Nosing – the leading edge of the tread
- Nosing Projection – overhang or protrusion, projection of the upper tread leading edge to the tread edge below.
- Stair Stringer – the main structural stair component, diagonal boards supporting and holding the treads and risers, transfers loads to the structure.
- Open Stringer – sawtooth stringer, zigzag shape (treads installation directly onto the stringers).
- – housed stringer (treads fit into routed channels in the stringer).
- Total Rise – the vertical distance from the lower finished floor level to the upper finished floor level
- Total Run – the horizontal length of stairway, from the end of the staircase with bottom stair nosing to the back of the riser on the top.
- Balustrade – railing system (the complete assembly of handrails, balusters, newel posts).
- Handrail – rail on top of the balusters for grasping with a hand
- Balusters – vertical columns supporting a handrail, spindles
- Newel Post – structural element of a staircase, vertical column connecting balustrade components, supporting the handrails, joining treads and stringers.
- Headroom – the clear vertical space between the ceiling and the nosing line (to prevent striking the head).
- Landing – platform at the top and bottom of the stairway, intermediate platform between flights, changing the direction of stairs.
- Nosing line , Pitch line – line connecting the nosings of the treads.
- Minimum stringer throat depth – stringer minimum width from the edge to the saw's teeth, it’s responsible for the structural capability (don’t overcut stair stringer)
- Flight – a stairway, uninterrupted series of steps between landings or levels
A typical staircase is shown below with the main stair parts:
Stair rule of thumb formulas for planning a comfortable staircase
In addition to min and max Building Code requirements there are a few formulas that can help to design a comfortable, and most importantly, an ergonomic staircase.
The fundamental rule for determining a safe and comfortable rise and run of a staircase is a formula invented by the French architect Francois Blondel in the 17th century, up till now it remains practically unchanged:
Blondel formula: 2×R+ G = 63 - 65 cm,
- R — step height (rise);
- G — step width (run, going);
- 63-65 cm — an average stride length of a person.
There are formulas for designing comfortable staircases among carpenters - Rule of thumb formulas:
- (Rise + Going) = 17 ½ - 18 inches (44.45 - 45.72 cm)
- (2 x Rise + Going) = 24 - 25 inches (60.96 - 63.5 cm)
- (Rise * Going) = 70 – 75 inches (177.8 - 190.5 cm)
According to the first two rules, ideal dimensions of a stair are 7” rise (17.78 cm) and 11” run (27.94cm - almost 28 cm). The stair angle should be 30 – 37 degrees.
Building Code and regulations
Now you are aware of main parts of staircase, basic terminology and rules for determining the comfortable stairs. But what is more important is that your design should be compliant with locally adopted Building Codes. There will be big problems in case of not upholding the requirements.
Every country has it’s own building regulations (even every state). So your stair should be compliant with:
- BCA (Building Code of Australia), if you live in Australia;
- UK Building Regulations 2010 Part K, if you live in the United Kingdom
- IRC (International Residential Code) for dwellings, for commercial stair standards IBC (International Building Code) – stair code of the United States of America
- NBC (National Building Code of India) – for India.
|Stair Type||Rise (R)||Going (G)||Slope Relationship (2R+G)|
|Stairs (other than spiral)||115||190||240||355||550||700|
The height of a balustrade or other barrier must be not less than 1 m above the floor of any access path, balcony, landing, etc, and not be less than 865 mm above the nosings of the stair treads or the floor of a ramp.
|Stair Type||Rise (R)||Going (G)||Slope Relationship (2R+G)|
|Private Stair 1,2||150||220||220||300||550||700|
|General Access Stair||150||170||250||400|
- The maximum pitch for a private stair is 42°
- For dwellings, external tapered steps and stairs that are part of the building, the going of each step should be a minimum of 280 mm.
Headroom - at least 2m.
|Dimension||part of IRC 2018||Min||Max|
|Rise (step height)||R3220.127.116.11||102 mm||4||196 mm||7 3/4|
|Going (run)||R318.104.22.168||254 mm||10||-|
|Nosing projection||R322.214.171.124||19 mm||3/4||32 mm||1 1/4|
|Handrail height||R3126.96.36.199||864 mm||34||965 mm||38|
|Headroom||R311.7.2||2032 mm||6 feet 8 inches||-|
|Dimension||part of IBC||Min||Max|
|Rise (step height)||1011.5.2||102 mm||4||178 mm||7|
|Going (run)||1011.5.2||279 mm||11||-|
|Nosing projection||1011.5.5.1||-||32 mm||1 1/4|
|Dimension||part of NBC 2016||Residential buildings||Other buildings||Low income Housings|
|Rise (step height)||188.8.131.52||190 mm||150 mm||200 mm|
|Going (run)||184.108.40.206||250 mm||300 mm||225 mm|
|Headroom||12.18.2||220 cm||210 cm|
|Stair width||220.127.116.11||1 m||1.5 - 2 m||0.6 m|