Stair stringer calculator: Calculate length and number of steps

Stairs are an integral part of a house or any structure. When constructing a staircase, one must consider different factors, such as the building codes, apat from parameters and calculations related to staircase length, width, height, placement of doors, etc. A stair calculator is useful when calculating these parameters related to staircase construction. Here is a guide.

What is a stair calculator?

A stair calculator is a digital tool used to calculate unit rise and run of stairs, stair elevation angle, stringer length, step height, tread depth and the number of steps required for a given run of stairs.

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Also read all about direction, location and number of steps as per staircase Vastu

Stair calculator: How to calculate stairs?

Let us assume a floor-to-floor level of 600 mm for determining stairs. For example, according to the building regulations, the riser height allowed is 150 mm to 220 mm.

Minimum riser height = 150 mm

Number of steps = overall change in level (overall rise)/ minimum riser height = 600/150 = 4

Thus, we can construct four risers or steps in the staircase.

*The rise and run calculator of a staircase is applicable for a single flight of stairs. In the case of a landing, every flight must be considered separately.

Stair calculator: Flush mount vs standard mount

It is also essential to determine if the staircase will be installed on a standard mount or a flush mount. The last tread of stairs is one step lower than the floor level in a standard mount, while it will be at the same height as the floor level in a flush mount.

Using the values of the rise and run of a step, you can calculate the remaining characteristics.

Check out these exterior staircase designs for Indian homes

How to calculate the run?

The number of stairs equals the total rise divided by the rise. If the height of the first step is different, it must be accounted for when calculating stairs.

Now, the total run = run x number of stairs

For a standard mount, you must deduct one from the number of stairs.

Stair stringer calculator

Stringer length is calculated based on the Pythagoras Theorem.

i.e., stringer length² = total run² + stinger height²

The stringer height = total rise in case of the flush mount to total rise in a standard mount.

See also: Beautiful staircase design ideas for your home

Stair angle calculator

The mathematical formula for calculating the stair angle is given below:

angle = arcsin (stringer height / stringer length)

Staircase terminology

Run or tread

It is a component of the staircase, on which a person steps when climbing stairs. The length of the run or a tread is calculated from the outer edge of a step, including the nosing, to the vertical surface called the rise. The length of the tread above the last riser is not included when calculating the total run of a staircase.

See also: Modern ideas for tiles for stairs in your house

Nosing

Nosing refers to the protrusion at a tread’s edge projecting over the riser in the lower level. The nosing is counted when measuring the tread’s length. However, the total run cannot be calculated basis the sum of tread length when nosing is present as the overhang caused should be subtracted from the total run.

Rise or riser

Riser is the height of the step calculated from the top of a tread to the top of the subsequent tread. It excludes the thickness of the tread. The number of risers is calculated to determine the number of staircase steps.

Stair stringer

It is a structural component of a staircase that supports the treads and risers. Normally, there are three stringers in a staircase – one placed on either side of the staircase and one at the centre.

Staircase width

The width is calculated from one edge to another edge of each side of the tread, perpendicular to tread length. Handrails are excluded from the calculation. Usually, the width is the longer side in staircases.

Headroom

Headroom refers to the height calculated from the top of a tread to the ceiling. The headroom is essential as it allows people to get enough space to move comfortably through stairs.

Handrails

A handrail refers to the railing running up the staircase incline and it is designed to provide support to people to safely climb or descend the staircase.

See also: A guide to choosing the right steel railing design for home stairs

Landing

The landing refers to the platform that connects two flights of stairs.

Stair calculator table

One can use the Stairs calculator to calculate unit rise and run of straight stairs.

•         Unit rise is 0.192 m
•         Unit run is 0.231 m (0.281 m incl. nosing projection)
•         Elevation angle is 39.8 degrees

How many steps will I need?

As per the Indian National Building Code, the minimum width for a staircase in a residential structure must be 3 feet and 6 inches while the tread without nosing must have a minimum width of 10 inches and 10 ¼ inches if nosing is required.

For a 12-feet high ceiling or floor in a building, there is a requirement of 21 stairs or steps or riser, 20 number of tread and about 14 feet of stringer to go up.

How to use stair stringer calculator?

A stair stringer calculator is available online. Before using the calculator, make sure you have the following details:

• Total height of stairs required
• Local maximum riser height as per the building code
• Local minimum riser height as per the building code
• Local minimum tread depth (run)
• Local minimum tread overhang, the length from the face of the riser to the front edge of the nosing
• Local maximum tread overhang, the length from the face of the riser to the front edge of the nosing

To use the calculator, input details such as the size of run in metres/centimetres, total rise in metres/centimetres to get details on the number of steps, stringer length, angle, etc.

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