# Stair Calculator

CASAPLORERTrusted & Transparent112.5 inStringer Length:

212.26 inStringer Width:

12.72 inAngle:

32.01°Step Rise:

7.5 inStep Run:

12 in

## About the Stair Calculator

This stair calculator helps you estimate the dimensions of the stairs in a simple way. Using total run and total rise, you can see how your stairs can look with a different number of steps that follow the most recent International Building Code requirements. It also can calculate two different types of stair mounts: Standard and Flush. This calculator allows you to input total run and total rise in the units of your choice and calculate the dimensions of the stairs in the unit of your choice by adjusting the “To Unit” variable.

## Definitions of Variables

This calculator uses multiple variables to create the dimensions necessary to understand how the stairs will look like. The following list explains all the variables used in the calculations.

Input Variables:

- Total Run

The total horizontal length of the stairs. - Total Rise

The total vertical length between the two floors. - Mount

The way stairs connect to the decking. The flush mount connects the decking and stairs on the same level. This means that the stairs will have the same height as the total rise. Standard mount, on the other hand, uses decking as an extra step. This means that the height of stairs will be one step lower than the total rise.

Output Variables:

- Stringer Height

Stringer Height refers to how high the stairs reach when the stringer is properly adjacent to the decking. In the case of the flush mount, the stringer height is equal to the total rise. On the other hand, the stringer height for the standard mount will be equal to the total rise minus the rise of one step because the decking is used as an extra step with this kind of mount. - Stringer Length

Stringer Height refers to how high the stairs reach when the stringer is properly adjacent to the decking. In the case of the flush mount, the stringer height is equal to the total rise. On the other hand, the stringer height for the standard mount will be equal to the total rise minus the rise of one step because the decking is used as an extra step with this kind of mount. - Stringer Width

Stringer width is another important variable for estimating the dimensions of materials needed to be purchased to make a stringer. Stringer width is the thickness of the stringer at its widest point. - Angle

The angle refers to the elevation angle of the stairs - Rise

A rise refers to the height of a single step. - Run

A run refers to the length of a single step.

## How to Calculate the Stairs Dimensions

To calculate the dimensions of stairs, there are quite a few formulas needed to be used. The calculations might look difficult, but following a step-by-step process described below, it is very simple to estimate all the required dimensions for the stairs. Since there are two ways how a staircase can be mounted, there are two separate sets of formulas to calculate the dimensions of the stairs.

To calculate the dimensions, you need to have the following variables:

- Total Rise
- Total Run
- The Number of Steps

Even though you can choose the number of steps you want, according to the International Building Code, a single step has to have a run of at least 10 in. and the rise of no more than 7.5 in. Given these requirements, to estimate the appropriate range of numbers of steps, the following formulas may be used:

You can pick any number of steps you want between the minimum and the maximum number of steps to comply with the requirements. If the maximum number of steps calculated is less than the minimum number of steps, it is impossible to comply with the requirements. In this case, you can construct the stairs at your own risk.

### Calculating for Standard Mount

- Calculate the Rise and Run of a Single Step

The standard mount uses the porch as a step. This implies that the number of runs will be equal to the number of rises minus one. The following formulas will help you calculate the rise and run of a single step: - Calculate Stringer Height

Stringer length can be calculated using a Pythagorean theorem, stringer height, and total run. - Calculate Stringer Length

Stringer length can be calculated using a Pythagorean theorem, stringer height, and total run. - Calculate Stringer Width

As a rule of thumb, a stringer width should be double the thickness of a single step. Because of that, the following equation is helpful to calculate stringer width. - Calculate Elevation Angle

The last metric that needs to be calculated is the elevation angle. The following formula will help you determine the angle.

### Calculating for Flush Mount

- Calculate the Rise and Run of a Single Step

The flush mount does not use the porch as a step, which means that there is an equal number of rises and runs on the stringer, and they are equal to the number of steps chosen. The following formulas will help you calculate the rise and run of a single step: - Calculate Stringer Height

Stringer refers to a frame of the stairs. Since flush mount does not use porch as an extra step, the height of the stringer is simply the total rise needed.

All the steps from 3 to 5 are the same for both, standard and flush mounts. If you calculate for a flush mount, you should find rise, run and stringer height for the flush mount and use the equations found in steps 3 to 5 of Calculating for Standard Mount to find all of the estimates.