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Stair Calculator

Enter the required measurements in their designated fields and the calculator will calculate various important entities to complete the staircase project.

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Determine different important parameters that are involved in the construction of stairs with the help of this free online stair calculator. Moreover, we will also take you through fraction and decimal values involved in the measurement criteria later on. So, let’s first discuss stair riser calculations.

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What Are Stairs?

“A particular structure that is built to connect two floors that are at large vertical distance.”

As it is not possible to cover this large distance by taking one step only, this structure is divided into smaller horizontal treads that are called steps. You can design stairs according to the map and space available. All you need to focus on is the angle that will keep stair design catchy and strong enough. No doubt all these calculations are pretty complex. That is why you can use our best stair angle calculator to carry out calculations and reduce the risk of any error.

Stair Terminologies:

Before we move ahead discussing the various stair calculation formulas, we must take a look at the following parameters that comprise together to raise a staircase:

Image of Stairs


As you know treadmill, a machine that you run on in the gym. Similar is the case with the treads of the staircase. The horizontal part of every step that you step on is known as the tread or run. Whenever you think of constructing a staircase, you can immediately get to know how many exact treads you need to cover the distance between the floors. You must be wandering that we just used the word immediately and did not discuss how it could happen. But wait… Let us tell you that you can do it with the assistance of a free online stair tread calculator.


The vertical distance between two successive treads/runs is called the rise.

Stair Stringer:

The base on which the steps are constructed is the stair stringer that could also be determined by the use of a free online stair stringer calculator.

Angle of Stairs:

Stair angle is very important to measure because the more balanced the angle is, the more it will be comfortable to go up and down without getting imbalanced. If you are going to construct a new house or building, ask your architect to make use of this stair angle calculator to determine the right inclination angle for the stairs.


It's a place where two sets of stairs meet. You can also consider it as the midway path between stairs.


It is the part of the run/tread that overhangs the riser of the stair.

Flush Mount:

In flush mount, the last step of the stairs is at the same level of the upper floor.

Standard Mount:

When it is about to construct a standard mount, then you will consider the last step always one step down from the level of the floor.


It is the distance between the end point of the ceiling and the tread right beneath it.


A particular support that allows you to avoid falling when going upstairs or downstairs. The free steps calculator is the one that is a handy and fast method to calculate all of the above parameters regarding stair structure.

Staircase Calculation Formulas:

What would happen if the stair measurements are not taken properly? Chances are there that the structure will fall down. That is why to avoid such failure issues, we must take into account the measurements exactly. Here our best stair calculator provides you with this facility as it automatically calculates all the factors that you may need for constructing the stairs. How does it sound to you?

Anyways, let us have a look of the following stair calculation formulas below:

Number of Stairs:

Number of Stairs = Total Rise / Rise

In case of standard mount:

Number of Stairs = Number of Stairs - 1

The free online stair stringer calculator also makes use of the same above formula to calculate the actual number of steps that will be enough to construct within the area provided.


Here you must keep one thing in mind that if the height of the very first step gets different from all others, you need to consider it individually in the calculations. We know that it may confuse you. That is why our step calculator automatically and instantly figures out such different calculations and lets you know if there are any changes to be made.

Total Run:

Once you calculate the number of steps or stairs, you can easily go for calculating the total run by subjecting to the following formula:

Total Run = Run * Number of Stairs

Stair Stringers Length:

You can easily compute the stair stringer length with either free stringer calculator or by using the pythagorean theorem:

Stringer Length² = Total Run² + Stinger Height²

Moreover, you can also simplify the various trigonometric ratios with the help of our pythagorean theorem calculator that will ease your calculations.

Stringer Height:

There arise two cases which are as follows:

In case you have flush mount, we have:

Stringer Height = Total Rise

In case you have standard mount:

Stringer Height = Total Rise - Rise

Staircase Angle:

Staircase angle is the most important factor while designing the staircase. It acts as a deciding factor for the life of the stair base. You can calculate this angle by subjecting to the following formula:

Angle = arcsin(Stringer Height / Stringer Length)

The free stair angle calculator makes use of the same above formula to estimate the best angle for setting up the staircase base.


It is the vertical distance between the furnished floor (Run) to the ceiling endpoint. You can determine the headroom with the help of the following expression below:

Headroom = Riser Length - Ceiling Thickness

For every four consecutive increases in the measure of distance to restriction, the headroom will be equal to riser addition to the answer obtained. It may confuse you a little bit, but do not worry. Our free stair calculator will do such calculations for you in a couple of clicks.

How To Calculate Stairs Parameters?

Let us go through an example in which we will calculate a certain stair element to clarify your concepts. Let’s go!


How to calculate stair stringers length when the height of stringer is 100 inches with a total run of 90 inches?


As we know that:

Stringer Length² = Total Run² + Stinger Height²

Stringer Length² = 90² + 100²

Stringer Length² = 8100 + 10000

Stringer Length² = 18100

Stringer Length = 135 inches (For under root calculations, tap square root calculator)

How Stair Calculator Works?

Get instant estimation of the elements that are included in the construction of stairs with the help of this free online stair rise and run calculator. Let’s go to learn together how it works!


  • First of all, select whether you want to perform calculations with “One Run” or “Total Run”
  • After doing so, go for entering all the parameters in their designated fields
  • Tap the calculate button


The free stairs calculator the following stair entities:

  • Rise measurement
  • Run measurement
  • 1st step rise
  • Total Run
  • Number of Steps
  • Stringer height
  • Stringer length
  • Inclination angle

If you want to make calculations in feet, you can use our online feet and inches calculator to convert inches to feet immediately.


What is a good run and rise for stairs?

According to the rule of thumb as set by the government of the USA, the standard rise length can be a maximum of 7 inches (17.78cm). While for tread/run, this length is about 11 inches (27.94cm). You can also account for these calculations by commencing to our best stair calculator within a couple of clicks.

What is the minimum head clearance for stairs?

The minimum head clearance for the stairs is about 84 inches that is measured from the corner of the upper ceiling to the run right below it.

What is the 18 rule for staircase?

Rule 18 states that the rise plus run length should be equal to 18 inches. This is because many people find such stair sizes more comfortable to step on.

Can I use 2 by 10 for stair stringer?

Within building code guidelines, it is a good stair dimension. But you must keep in mind that the stair width at the narrowest side should not be less than 3.5 inches. Moreover, you can get standard stair computations by making use of the free stair calculator.

What size lumber is used for stair stringers?

The stair stringer usually makes up the base of your stair structure. That is why you are required to use 2 by 12’s stair stringers that are of high quality and properly pressure treated.

Do you install a riser or tread first?

Wherever you go for constructing stairs, build up the riser first. After that, construct alternative risers and treads until they are made to meet the ceiling floor. For best stair dimensions, let our stair calculator perform various calculations immediately and display on your screen.


As we know that stairs are the building block to connect two levels, so you should always go for estimating the most accurate stair dimensions that will best suit your house design and architecture. Not only this, using the free stair calculator will let you design such a staircase that will be easy to ascend and descend by everyone.


From the source of Wikipedia: Stairs, Components and terms, The railing system, Measurements, Stairs and art, Notable sets of stairs

From the source of inspectapedia: Stair Rise, Stair Building Calculations, Stairway Run

Other Languague: Výpočet Schodiště, Kalkulator Schodów, Калькулятор Лестницы, Calcular Escalera, Merdiven Hesaplama, Calculer Escalier, Calculo De Escada 

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