When you've climbed a flight of stairs it's rather common to wonder about the number of steps you've covered.
Climbing a step on stairs is considered equivalent to taking 3.8 steps on level ground due to the extra effort required.
The number of steps in a flight of stairs is generally 13 to 15. This number is found to be rather common due to the ceiling height being either 8 ft. or 9 ft. for most buildings.
What is a Flight of Stairs?
A flight of stairs refers to an uninterrupted series of steps between two landings.
Every step has a tread and riser that measures a standard size set by building codes.
How Many Steps In A Flight Of Stairs?
The number of steps in a flight of stairs is determined by the height difference between the floors, and the tread and rise sizes used.
According to the International Residential Code 2018, the maximum vertical rise allowed for a flight of stairs is 151 inches (3835 mm) between floor levels or landings.
The same standards set the minimum depth for stair treads as 10 inches (254 mm) and the maximum riser height as 7 ¾ inches (196 mm).
While these are the limits set by the code, typically the numbers used are much less harsh to make users comfortable.
|Maximum Vertical Rise||151|
|Riser Height||7 ¾|
Stair Dimension Limits (IRC 2018)
Calculating the Number of Steps
Number steps = (Ceiling Height or Vertical Rise between landings) / Riser Height
If you get a fraction or decimal, you need to round it up to the closest number.
A typical home in the USA has a ceiling height of either 8 feet (2438 mm) or 9 feet (2743.2 mm).
This ceiling height means the number of steps is usually either 13 or 14 or 15 in most homes with each step having a uniform riser height.
While this is typical, sometimes apartments and certain buildings can have higher ceiling heights such as 10.5 ft.
In such a case, the number of steps increases to 18.
Stairs are divided into two flights of 9 steps each in such a case, with a landing in between.
Although residential codes place these limits on stair measurements, the number of steps in a single flight can be much higher in industrial buildings often running above 20.
This is primarily due to space constraints that set a minimum limit on the riser height.
It's not comfortable nor very healthy to climb those many steps on a regular basis.
Number of Steps for 8-foot Ceilings
8-foot ceilings were the norm a few decades back in the USA due to multiple reasons.
One was that timber was milled in 8 feet lengths, and that made this height the natural choice for ceilings.
Another reason for a short ceiling height was to reduce the heating costs.
Even now, 8 ft. ceilings are legally allowed as the minimum ceiling height prescribed by the international residential code (2018).
Considering the maximum riser height set by the code, which is 7-¾" (196 mm), the minimum number of steps for an 8 feet ceiling home is 13 steps.
As you reduce the riser height, the horizontal distance occupied by the stairs increases.
Therefore if you have a lot of space in your building, you can choose a lower riser height to ease the effort of users.
However, the minimum riser height you need to give is 4" (101 mm).
If you use a 4" riser height, you'll end up with 24 steps.
But with a short riser height, people tend to climb two steps at a time, defeating the purpose of easing the riser height.
All things considered, the typical number of steps is 13 or 14 steps for 8 ft. high ceilings with either 190 mm or 175 mm riser heights.
Number of Steps for 9-foot Ceilings
Most modern homes in the USA are now built with a 9 feet ceiling height an upgrade from the 8 ft. ceilings of the previous decades.
The minimum number of steps, in this case, is 14 considering the maximum riser height of 7-¾" (196 mm).
The typical number of steps to give is 14, 15, or 16 considering different riser heights for 9-foot ceiling height.
Number of Steps Required for 9ft Ceiling (IRC 2018)
Number of Steps for 10-foot Ceilings
10 feet ceilings are used when you want a spacious, grander feel for your room.
The downside is that you incur higher heating and cooling costs.
In terms of the number of steps, the minimum number of steps here is 16.
However, it's typical to have 17 or 18 steps for 10 ft. ceiling height buildings.
18 steps are usually not given in a single flight of stairs, and rather are divided into two flights of 9 steps each with a landing in between.
Thus when you design a building with a 10 ft. high ceiling, consider the increase in space occupied by the stairs too due to the rise in the number of steps.
|Ceiling Height||Minimum Steps||Typical Steps|
Number of Steps Required for 10ft Ceiling (IRC 2018)
What Is the Minimum Number of Steps in One Flight?
While there is no explicit mention of a minimum number of steps in any of the codes, it's possible to arrive at a number for a particular ceiling height.
For a 9 ft ceiling height, considering the maximum riser height of 7-¾" (196 mm), the minimum number of steps you need to have in a flight of stairs is 14.
If you consider the maximum allowed vertical rise for a flight of stairs, i.e. 12.6 ft. (3835 mm), the minimum number of steps you need is 20 steps.
|Maximum Vertical Rise||Minimum Steps|
Number of Steps Required for 12.6ft Vertical Rise (IRC 2018).
What is the Maximum Number of Steps in a Flight of Stairs?
The maximum number of steps in a flight can be calculated by considering the lowest allowed riser height.
According to International Residential Code 2018, the minimum riser height allowed is 4 inches (101.6 mm).
For a 9 ft ceiling height, considering the minimum riser height of 4 inches (101.6 mm), the maximum number of steps you can have in a flight of stairs is 27.
Number of Steps Required for 9ft Ceiling (IRC 2018).
However, for ergonomics, any stair having 18 or more steps should be divided into two flights with a landing in between.
If you consider the maximum allowed vertical rise for a flight of stairs, i.e. 12.6 ft. (3835 mm), the maximum number of steps you can have is 38 steps.
|Maximum Vertical Rise||Steps|
Number of Steps Required for 12.6ft Vertical Rise (IRC 2018).
How Long is a Flight of Stairs?
The stair length or total run of a flight of stairs is the sum of the tread lengths of all the steps.
According to the international residential code 2018, the minimum tread length (also called depth) to be used for a step is 10 inches (254 mm).
While a lot of older homes use tread lengths less than this, all new residential buildings should comply with this minimum tread length rule.
If you consider a 10-inch tread length for all your steps, and the number of steps as 13, the length of a flight of stairs works out to 130 inches (3302 mm).
As the stair length increases, the cost of trim such as stair skirtboards increases proportionally.
An important point to note when measuring tread length is to subtract the length of the nosing projection from the overall length.
The minimum tread length of 10 inches holds true only if there is a nosing projection for the tread.
In case there is no nosing projection, the minimum tread length to have is 11 inches (280 mm).
There are standards for nosing projections as well.
Any nosing projection should be between ¼ inches and ¾ inches in length.
Sometimes, contractors adjust the tread lengths resulting in multiple tread lengths in the same flight of stairs.
In such a case, IRC specifies that the greatest tread length shall not exceed the smallest tread length by more than 3/8 inches.
Length of Staircase for 8-Foot Ceiling
As explained in a previous section, an 8-foot ceiling usually has 13 or 14 steps.
Using the minimum tread length of 10 inches, the length of the staircase for an 8-foot ceiling works out to 130 inches (3302 mm) or 140 inches (3556 mm).
Length of Staircase for 9-Foot Ceiling
A 9-foot ceiling building typically has between 14 to 16 steps in a flight of stairs.
Using the minimum tread length of 10 inches, the length of the staircase for a 9-foot ceiling works out to between 140 inches (3556 mm) to 160 inches (4064 mm).
Length of Staircase for 10-Foot Ceiling
A 9-foot ceiling building typically has between 17 to 18 steps in a flight of stairs.
Using the minimum tread length of 10 inches, the length of the staircase for a 10-foot ceiling works out to between 170 inches (4318 mm) to 180 inches (4572 mm).
However, 18-step stairs are usually divided into two flights with a landing in between.
Therefore the stair length in a single flight of stairs gets halved to 90 inches (2286 mm).
Maximum Length of a Flight of Stairs
The international residential code places no restrictions on the maximum tread length that can be used on stairs.
Therefore there is no theoretical limit on the length of a flight of stairs.
Practically, more tread length means more area occupied by the stairs and less room for other things in the building.
This means designers or contractors rarely have tread depths larger than 11 inches.
The length of stairs that you can have is also limited by other components you might have in your building like walls and columns.
IRC also specifies a minimum length for landings where the stairway has a straight run.
The depth of landing in the direction of travel shall be not less than 36 inches (914 mm).
The depth of landing required also limits the length of a flight of stairs as only the length after accommodating the landing is available for stairs.
The number of steps you should have in your home or building should be based on the space available and your ceiling height.
For obtaining permits and reasons of safety, you also need to comply with the residential code requirements insisted by your local approving authority.
The standards in the building codes have been arrived upon through years of research and revisions.
Following those standards will likely result in the best experience for users of the stairs as well.
Frequently Asked Questions (FAQ)
How many steps is 50 flights of stairs?
Typically a flight of stairs has 13-15 steps. This means 50 flights of stairs will most likely have 650 to 750 steps.
What is considered one flight of stairs?
One flight of stairs is a term used for a series of steps that are continuous, between two landings or floors. There is no fixed number of steps for a flight of stairs and it can vary considerably.