Stair Dimensions: What is the Standard Size & Measurements?

Last Updated on September 13, 2023 by Kimberly Crawford

Stair dimensions are more than just measurements; they are vital factors that contribute to the safety and comfort of every step we take. Whether you’re ascending to the next floor in your home or descending a staircase in a public building, the dimensions of those stairs play a significant role in ensuring a safe and comfortable journey.

Stair dimensions include various key elements such as the width of the stair, the height and depth of each step, and the overall incline of the staircase.

Each one of these elements needs to be carefully considered and accurately measured during the design and construction process. If the dimensions are off, even slightly, it could result in an uncomfortable climb or worse, a hazardous fall.

Standard stair dimensions, which have been established through years of architectural practice and regulatory standards, provide a guideline for builders and designers.

These standards ensure that stairs are built to a size that the majority of people can use safely and comfortably. Understanding these standard dimensions is essential whether you’re designing a new staircase or checking the safety of an existing one.

In this article, we will delve deeper into the importance of stair dimensions, discuss the standard measurements, and explore how these dimensions impact safety and comfort. We’ll also touch upon how these dimensions can be calculated and adjusted to meet specific requirements. So, let’s step into the world of stair dimensions.

Understanding Stair Terminology

When discussing stair dimensions, there are several key terms that you should be familiar with:

  1. Tread: This is the horizontal part of the stair where you place your feet. It’s essentially the flat surface that you step on when climbing or descending the stairs.
  2. Riser: The riser is the vertical portion between each tread. In simpler terms, it’s the part of the stair that rises from one step to the next.
  3. Run: The run is the horizontal distance from the front edge of one tread to the front edge of the next tread up. It does not include the overhang of the nosing.
  4. Nosing: The nosing is the protruding edge of the tread that hangs over the riser beneath. Not all stair designs have a nosing, but when they do, it can help to make the stairs safer by reducing the likelihood of slipping.
  5. Stair Width: The width refers to the measurement from one side of the stairs to the other, usually taken from the outer edges of the handrails.
  6. Stair Height: Also known as the rise, the stair height is the vertical distance from the bottom of the first tread to the top of the final tread.
  7. Incline: The incline or slope of a staircase is determined by the ratio of the rise to the run.

Standard Stair Dimensions

stair size

Residential Stairs

Residential stair dimensions are often guided by local building codes designed to ensure safety and usability.

The minimum width for stairways in residential settings is generally 36 inches clear, meaning the space measured above the handrail. Handrails, when introduced, should not project more than 4 ½ inches on either side.

As for the individual steps, the riser height should be a maximum of 7-3/4 inches, while the tread depth (run) isn’t usually specified but should be comfortable for the average foot, which typically means around 10 inches.

Moreover, the headroom, or vertical distance from the top of the tread to the ceiling above, should be a minimum of 6′ 8″.

Commercial/Public Stairs

For stairs in public spaces, the minimum width usually increases. The general rule is a minimum of 44 inches, unless the stairway serves an occupant load of less than 50, in which case the minimum width is the same as that for residential stairs.

The other dimensions, such as riser height and tread depth, generally follow similar guidelines as residential stairs. However, commercial stairs may have additional requirements for elements like handrails and nosing to ensure better safety for a larger and more diverse group of users.

Variation by Region

It’s important to note that these are general standards, and specific requirements can vary by country, state, or even city. For instance, some codes like CA/OSHA specify a minimum stairway width of 24 inches. Therefore, always check with your local building code authority to ensure compliance with all relevant regulations.

Factors Influencing Stair Dimensions

Space Availability

Space availability is one of the most significant factors that influence the dimensions of a staircase. The available length, width, and height in the area where the stairs will be installed can limit the size and shape of the staircase.

For example, in a home with limited space, a spiral staircase or a steep staircase with small treads might be necessary to fit within the available space. However, in a larger space, there can be more flexibility to design wider, more gradual stairs that can be easier and safer to use.

Building Codes

Building codes play a crucial role in determining stair dimensions. These codes are set by local, regional, or national authorities to ensure safety and accessibility.

They specify minimum and maximum dimensions for elements like the riser height, tread depth, stair width, and headroom. Failing to comply with these codes can result in legal issues and safety risks.

User Needs

The needs of the users who will be using the stairs also significantly impact the dimensions. For instance, in a building where elderly people or children are likely to be frequent users, the stairs might need to be designed with smaller risers and larger treads to make them easier and safer to climb.

Similarly, buildings that need to be accessible for wheelchair users or people with mobility impairments may require ramps or lifts in addition to or instead of traditional stairs. In such cases, the dimensions of these features would be guided by accessibility standards and the specific needs of the users.

Calculating Stair Dimensions

Calculating stair dimensions involves determining the best riser height and tread depth for your staircase. Here’s a step-by-step guide:

Step 1: Measure Total Rise

The total rise is the vertical distance from the floor level of one floor to the next. Measure this distance.

Example: Let’s say you have a total rise of 105 inches from the first floor to the second floor.

Step 2: Determine Ideal Riser Height

Building codes typically recommend a maximum riser height of 7 to 7-3/4 inches. Choose a riser height within this range that suits your needs.

Example: We’ll choose a riser height of 7 inches for our example.

Step 3: Calculate Number of Risers

Divide the total rise by the chosen riser height. If the result isn’t a whole number, round it to the nearest whole number. This gives you the number of risers needed.

Example: 105 inches (total rise) divided by 7 inches (riser height) equals 15 risers.

Step 4: Adjust Riser Height

Divide the total rise again by the number of risers to get the exact riser height. This might be slightly different from the height you chose in step 2 due to rounding.

Example: 105 inches (total rise) divided by 15 (number of risers) gives a final riser height of 7 inches.

Step 5: Calculate Tread Depth (Run)

Building codes usually recommend a minimum tread depth of 10 inches. The tread depth, along with the riser height, should be comfortable for the average person to step on. A commonly used formula is “Riser height + Tread depth = 17 to 18 inches.”

Example: In this case, we have a riser height of 7 inches, so our tread depth will be 10 inches (17 – 7 = 10).

Step 6: Calculate Number of Treads

The number of treads is usually one less than the number of risers for most staircases.

Example: For our staircase with 15 risers, we’ll have 14 treads.

Safety Considerations for Stair Dimensions

Stair dimensions play a crucial role in ensuring safety for users. Incorrect stair dimensions can lead to accidents, including trips and falls, which can cause serious injuries.

Relationship Between Stair Dimensions and Safety

The key elements of stair dimensions that impact safety are the tread width (the horizontal part where you step) and the riser height (the vertical part between each step). According to the International Building Code, the minimum tread depth should be 11 inches (280 mm), and the maximum riser height should be 7 3/4 inches (196 mm).

A consistent riser height and tread width throughout the staircase is critically important for safety. Our bodies develop a rhythm when climbing or descending stairs, and any unexpected variation can result in a misstep and potential fall.

Common Issues Caused by Incorrect Stair Dimensions

  1. Tripping and Falling: Inconsistent or too high riser heights can cause people to trip, while too low can cause them to lose their balance. Similarly, narrow treads don’t provide enough space for the entire foot, increasing the risk of slips and falls.
  2. Difficulty in Use: Stairs that are too steep can be difficult to climb, especially for children, the elderly, and people with mobility issues. This can also increase the risk of accidents.
  3. Fatigue and Discomfort: Incorrect stair dimensions can make using stairs tiring and uncomfortable, discouraging their use.

Solutions and Precautions

  1. Adhere to Building Codes: Ensure your stairs meet the minimum requirements set out in your local building codes. These standards are designed with safety in mind.
  2. Consistency: Make sure all the risers and treads on a staircase are of consistent height and depth. Even a small variation can cause trips and falls.
  3. Handrails: Install handrails on both sides of the staircase. They provide support and balance, especially for those who need it.
  4. Lighting: Proper lighting is essential to help people see the stairs clearly and avoid missteps.
  5. Non-Slip Surfaces: Use materials with good grip for treads to prevent slips, especially when the stairs are wet.
  6. Regular Maintenance: Regularly check for any wear and tear or damage to the stairs that could create an uneven surface or other hazards.

Design Considerations for Stair Dimensions

Stair dimensions can significantly impact the aesthetic and functionality of a space. They can either enhance or compromise the overall design, depending on how they’re integrated into the layout. Here are some key considerations for designing stairs and how different options can affect space.

1. Stair Width

The width of the stairs can influence the perception of the space. Wider stairs often create a grand, open feel, making them ideal for entryways or central locations in a home or building. The International Building Code (IBC) recommends a minimum stair width of 44 inches for commercial buildings and 36 inches for residential buildings.

2. Stair Height and Depth

The height and depth of each stair, also known as the riser and tread, can impact comfort and safety. A common recommendation is a riser height of 7 inches and a tread depth of 11 inches. These dimensions provide a balanced step that isn’t too steep or shallow.

3. Spiral Stairs

Spiral stairs are a popular choice for spaces with limited square footage. They add a unique aesthetic element but come with specific dimension requirements. The IBC suggests a minimum stair width of 26 inches, with each tread having a minimum depth of 7.5 inches at a point 12 inches from the narrower edge.

4. Floating Stairs

Floating stairs can create a modern, minimalist aesthetic. These stairs appear to float because their supports are hidden or minimal. However, they require precise engineering and construction to ensure safety. The dimensions will depend on the material used and the structure of the building but should still adhere to the standard riser and tread sizes for comfort and safety.

5. Split-Level Stairs

Split-level stairs add visual interest and can break up large, open spaces effectively. They require more space than a straight staircase but can incorporate landings that add functionality. The dimensions of split-level stairs depend on the overall height that needs to be climbed and the available floor area.


In conclusion, the dimensions of stairs play a vital role in both aesthetics and functionality. They can significantly influence the overall look and feel of a space, creating impressions ranging from grandeur to minimalism. Beyond aesthetics, the correct dimensions ensure comfort and safety for users, making them an essential consideration in any building or home design.

Different stair designs come with their unique dimension requirements, each suitable for specific spaces and aesthetic goals. Whether it’s the sweeping elegance of wide stairs, the space-saving efficiency of spiral stairs, the modern appeal of floating stairs, or the visual interest of split-level stairs, each design option offers its unique advantages.

However, regardless of the design chosen, it is crucial to adhere to recommended standards and building codes. These guidelines exist to ensure that stairs are safe and comfortable to use.

So whether you’re designing a new space or evaluating existing stairs, remember to consider these factors. The right stair dimensions can enhance your space’s design while ensuring it remains practical and safe for all who use it.

Don’t underestimate the power of well-designed stairs – they’re more than just a means of moving from one level to another. They can be a central feature that ties your space together, so give them the thought and consideration they deserve.