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How Big Is a Spiral Staircase? (Explained)

Spiral staircases are the most attractive and exquisite type of stairwell that has been utilized since antiquity. Even in current times, spiral staircases are used to provide a sophisticated representation of any interior.

Let’s see how big a spiral staircase may get, as well as some of the most intriguing facts and other frequently asked questions (FAQs) about it.

How big is a spiral staircase?

In terms of height, a spiral staircase is generally 3’6″ tall. Generally, it has a diameter ranging from 40-78 inches. Depending on the type of home you have, the height and diameter may vary. You may also measure your spiral staircase based on its thread size, footprint, and floor-to-floor height.

Several parameters may be used to evaluate a spiral staircase. It may be measured in terms of its opening space, floor height, spiral rotation, and platform sizes.

Let’s take a look at how wide, deep, and long a standard spiral staircase is.


The width of a spiral staircase dictates how comfortably it may be walked down.

A spiral staircase should be at least 5 feet wide, i.e., 60 inches, according to the International Building Code. However, nowadays, spiral staircases may be up to 6′, i.e., 72 inches wide on average.

But, this width might vary based on the living space of your home and other relevant parameters.


Many of us misunderstand the terms “depth” and “height” and whether they refer to the same measurement parameters or not. But, for the sake of clarity, let us assist you in resolving this ambiguity once and for all.

The vertical magnitude of an item is represented by both depth and height. As a result, particularly in the case of spiral staircases, the depth and height have the same meaning.

A spiral staircase’s depth, or height, should be at least 44 inches. It may differ for a variety of reasons, including your own preferences and bespoke home décor.


The length of a spiral staircase may be calculated using a variety of parameters. It may also differ depending on the size of your living space.

The typical length of a spiral staircase is between 3′-5″ and 3′-6″, i.e., 42-44 inches. However, this is the simplest and shortest length a spiral staircase may have.

What are the recommended dimensions for a spiral staircase? 

The required dimensions are based on the minimal range, which is too important for a spiral staircase. For starters, a spiral staircase should have a minimum height of 42-44 inches. With 9 threads, the minimum rotation should be 270o (1 thread = 30o turn).

Secondly, a spiral staircase’s minimum diameter should be 3 feet, 6 inches. Furthermore, in the event of a well opening, the minimum range should be 44×44 inches.

A minimum thread diameter of 3’6” and a thread depth of at least 7.5 inches are required (as per the national building code in the USA).

Do spiral staircases take up less space? 

Spiral stairs do, in fact, take up less space than traditional straight staircases. Spiral staircases were eventually created to conserve space in the first place. As a result, its key role is to conserve space in exchange for increased benefits.

Because of their tiny and circular form and size, they take up very little room in any place, saving up to 6-7 square feet.

Spiral staircases with a clockwise direction have been utilized since ancient times for their adaptability of placement, frequently in congested and confined locations. It is also acquiring a lot of prominence in recent times because of its unique property of taking up less room.

One of the primary reasons that spiral staircases take up less space is that all of the stairs are contained inside a set circle of spiral staircases, irrespective of their height.

As a result, if you want to preserve some extra space in your living room, a spiral staircase is the most fashionable option for a sophisticated interior design in both home and commercial areas.

How much room do you need for a spiral staircase? How big of an opening do you need for a spiral staircase?

To determine the measurement of how much area you will be needing for a spiral staircase, you need to follow certain prerequisites. For this, the footprint is used to determine the size of the room or space.

The term “footprint” refers to the amount of area that your stairwell typically takes up. If you can discover the footprint of your spiral staircase using a measuring scale, you may quickly determine how much space it requires.

Usually, the required room for any spiral staircase starts at 3 feet and 5 inches, which is, to be accurate, 42×42 inches. Again, you can take up this space for your stairs based on how big of a spiral staircase you want for yourself.

Thus, a 4-foot step will require almost 48×48 inches of area. Likewise, 4.6 feet, 5 feet, 5.6 feet, and 6.0 feet, respectively, will take up 48×48 inches, 54×54 inches, 60×60 inches, and 66×66 inches of area. It is consistently increasing by six inches each time with respect to the diameter.

A spiral staircase’s needed opening is 44×44 inches, or 3 feet 6 inches. Allow an extra 2-4 inches in the opening area for hand motions and the placement of the railings next to the spiral staircase.

How to size a spiral staircase? How to calculate spiral staircase dimensions? 

Now, let us know how to size a spiral staircase and how to calculate its dimensions through some easy steps.

Measure the overall floor-to-floor height:

The first and most important step in sizing a spiral staircase is to determine the total height between the upper and lower floors.

Take a tape measuring tool and measure from the lower ground level to the upper ground floor. Your spiral staircase’s lowest height might be anything from 86 to 144 inches.

The actual size of your staircase will be determined by the height calculation.

Calculate the diameter:

After choosing the height, bear in mind that your spiral staircase should have a diameter of at least 2.1 feet to 2.3 feet (26- 28 inches). This is the smallest diameter range that a staircase can have. 

To ensure simple hand motions and proper placement of the handrails on your staircase, add 1-2 inches to the initial diameter. Therefore, the new diameter will be 28+2=30 inches.

Determine the size of the threads:

Following the completion of the stairwell’s diameter calculation, the size of the threads must be determined.

As per the national building code in the United States of America, the thread depth of a spiral stairwell should be at least 7.5 inches at the wide end and 12 inches at the narrow end.

Let us consider that the height of the stairwell here is 88 inches. Thus, its thread count will be 9. But, regardless of the size of your threads, it should be 7.5 inches deep.

Find the number of steps:

As 7 is taken as the ideal range of vertical distance between every step, divide the previously determined height by 7. If the result is in decimal, take its nearest whole number.

For example, if the height of the stairs is 88 inches and it is divided by 7, the result is 12.57, i.e., 13 steps approximately.

That is how you calculate the number of steps on a spiral staircase. Don’t forget to add or subtract the number of steps as per the guidelines of the national building code.

Calculate the spacing between each steps:

After finding the number of steps, calculate the spacing between each step by dividing the total height of the spiral staircase with the number of steps.


88/13=6.76 inches

Therefore, the spacing between each step should be 6.76 inches.

How to choose a spiral staircase size?

The following is a list of ways in which you can choose the size of a spiral staircase:

Examining the chosen location:

It is very important to examine the location where you have chosen to build the spiral staircase. On its height, the size of the staircase is dependent.

Otherwise, if the size of the spiral staircase is bigger than the height of your chosen location, the stairs will not fit properly.

Considering the area of your living space:

The area of your living space is another important factor in choosing the size of the spiral staircase. If you have a large living space, then you might choose a spiral staircase of a large size accordingly.

But, if you have a small living space, you need to choose a small spiral staircase to accommodate it in your living space.

Final Thoughts 

A spiral staircase is approximately 3’6″ in height and has a diameter of 40 to 78 inches. You may also measure the many variables of a spiral staircase to calculate its size and to determine how big it is. However, the height and diameter may differ depending on the type of accommodation you have.