Stair Dimensions Australia Calculator
Chiquita Palafox
The Stair Calculator is an online tool for calculating various parameters involved in the construction of stairs. Refer to the figure adjacent to the calculator as a reference. A fraction to decimal conversion table for common fractions used in measurements is also provided at the bottom of the page.
Stairs come in many different forms, and while building a basic staircase may appear to be a simple task, there are actually a number of parameters, calculations, and building codes that must be considered. These range from the length, width, and height of specific parts of the stairs, to where doors are placed in relation to stairs; the arc of a door must be completely on the landing or floor and not be allowed to swing over steps. Below is a list of some of the most common terminology regarding stairs, as well as some commonly used building codes. Building codes or requirements can differ at a local level, and a person building a staircase should refer to the codes specific to their locations.
Run/Tread: The run or tread is the part of the stairway that a person steps on. Its length is measured from the outer edge of the step, which includes the nosing if it is present, to the vertical portion of the stair called the riser. Both nosing and riser are discussed below. When measuring the total run of a staircase, the length of the tread above the last riser is not included in the measurement. Also, when nosing is present, the total run is not simply the sum of tread length, since the overhang caused by the nosing must be subtracted from the total run.
Rise/Riser: The rise, or height of a step is measured from the top of one tread to the top of the next tread. It is not the physical height of the riser because this excludes the thickness of the tread. The number of risers, not the number of treads, is used to determine the number of steps that comprise a staircase.
Nosing: The nosing is the protrusion at the edge of a tread that hangs over the riser below. Not all steps have a nosing, but when present, the nosing is included in the length of the tread. The main purpose of nosing is to improve safety by providing extra space on which a person can place their feet.
Headroom: Headroom is the height measured from the top of a tread to the ceiling above it. While building codes for headroom are primarily intended to ensure enough room for people to comfortably use the stairs, the codes typically require far more room than the average height of a person to allow for moving larger objects such as furniture.
Stair Width: Stair width is measured from edge to edge of each side of the tread, perpendicular to tread length. While measurements of length are conventionally longer than those of width when considering rectangles, in the case of steps, the width is usually the longer side. Stair width does not include handrails.
Handrails & Guards/Guardrails: A handrail is a railing that runs up a stair incline for users to hold when ascending or descending a staircase. A guard is "a building component or a system of building components located near the open sides of elevated walking surfaces that minimizes the possibility of a fall from the walking surface to the lower level." Guards can include rails (guardrails), but can be any number of other constructions such as walls, half-walls, or even a bench.
Stringer: A stair stringer is a structural member that supports the treads and risers of a staircase. Typically, there are three in a staircase: one on each side, and one in the middle. Stringers are not always visible, but can be seen on stairs with open sides. The stringers can either be cut to the shape of each step, or in some cases, are uncut and conceal the edges of the treads.
The Stair Calculator Metric is the Metric version of mycarpentry.com's Imperial (inches) Stair Calculator and is used for calculating stair rise and run, stair angle, stringer length, step height, tread depth, and the number of steps required for a given run of stairs, but displays the results in millimeters. For convenience and flexibility, this metric stair stringer calculator comes in two forms: automatic and manual. Click on the [?] icons to determine the best calculator for your stairs.
Stringer - The stringer is the structural part of a set of stairs. They are 2x12s (or larger) material - the uncut portion of the stringer should not be less than 127 millimeters (5 inches). In a set of stairs, 915 millimeters (36 inches) wide, there are typically three stringers (one stringer on each side and one in the middle). The stringer length is the tip-to-tip length of the cut stringer. The Stringer Length value is the minimum length of 2x12 material required to lay out the stair stringer.
Total Rise [A] - The Total Rise is the vertical distance between the bottom of the first step and the top of the finished landing. The Total Rise should be no larger than 3835 millimeters (151 inches) between landings or floor levels.
Risers - The Step Height [F] is the typical height of each step. Code states that this should not be greater than 194 millimeters (7 3/4 inches). In a given run of stairs, the Step Heights should not vary more than 9.5 millimeters (3/8 inch). Open risers with openings more than 762 millimeters (30 inches) vertical to the floor should not permit the passage of a 102-millimeter diameter (4 inches) sphere.
Height of First Step [E] - The actual finished height of the first step is the same as the Typical Step Height [F], but when you cut the stair stringer, the First Step Height [E] is always the Step Height [F] minus the Tread Thickness [C].
Treads - The minimum Tread Depth [B] should be not less than 254 millimeters (10 inches). In a given run of stairs, the Tread Depth [B] should not vary by more than 9.5 millimeters (3/8 inches). Typically, stair treads are either a single 2x12 or two 2x6s.
Number of Steps (Risers) - The number of risers is not necessarily the same as the Steps on Stringer [D]. If the Stinger Mount Type is Flush, then the number of risers is the same as the number of steps. If the Stinger Mount Type is Standard, the number of risers will be one more than the number of Steps on Stringer [D].
Stairs and Landings - Landings break up long runs of stairs. The building code states that the minimum width of a landing should not be less than the width of the flight of stairs served. **"Where the stairway has a straight run, the depth in the direction of travel shall be not less than 914 millimeters (36 inches)." For additional information, check out Stairs with Landings.
Use the Automatic Calculator if the only crucial factor in your stair design is the Total Rise [A]. Using a few (modifiable) default settings, the automatic calculator will compute all of the other factors, including the Total Run [G].
The Total Rise [A] is the finished height of your landing or deck. The TargetStep Height [F], is the height that you would like your steps to be. The automatic calculator will design your stair stringer as close to the target height as possible, while maintaining a common step height. You can also alter the Tread Thickness [C] and Tread Depth [B] as needed. Follow the steps below to design your stair stringer:
Once the stair results have been calculated, you can toggle between the Standardand Flush options to compare the differences. Since the Tread Depth [B] is a constant, when using the Automatic Stair Calculator, the Total Run [G] will vary when you toggle between the two mount options.
Once you determine the Total Rise, Total Run, and Tread Thickness, the most important variable is the Number of Steps. The first time you enter a value in the Number of Steps field, it will likely be a guess. Each time you change the Number of Steps value and recalculate, make note of the Step Height and Tread Depth. If the numbers are too high, add some more steps. Building codes suggest Step Height [F] be no more than 7 3/4" and the Tread Depth [B] be no less than 10".
Once the stair results have been calculated, you can toggle between the Standardand Flush options to compare the results. Unlike the Automatic Calculator, you will notice that the Tread Depth [B] will vary on the Manual Stair Calculator because the Total Run [G] is a constant and the Tread Depth [B] is a variable.
No two sets of stairs are the same, they take many different shapes. Building a staircase on face value may appear to be a simple job, there are many variables, calculations and building codes that need to be considered before starting construction. The specifications for stairs encompass various elements, including the required dimensions such as maximum rise height, minimum rise height, and going length. With customers around around the world, the Chippy Tools stair calculator allows for these specifications to be modified to account for applicable building codes in your region.
If you have set the stair dimensions correctly and want to adjust the step amount use "Clear A & B & Steps values" button and re-enter the new step value and re-press the "Calculate" button. to receive your results
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Having two steps will give us a rise of 225mm which according to the regulations above would be over the maximum allowance for a riser. So in this case we have to have a riser of 150mm giving 3 steps.
For general access stairs a maximum allowance of 12 steps before a landing is required. With utility stairs, a maximum of 16 steps is allowed before a landing. In no circumstances should there be a single step, so it is better to balance out the landing position so that there are at least two or more steps either side of the landing.
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