# Stair Calculator Metric

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 to use for your stairs.

## Automatic Stair Calculator Metric

Input: Total Rise [A] (ex: 1525) (mm)
Target Step Height [F] (mm)

Stair Results:
Number of Steps (risers)
Steps on Stringer [D]
Height of First Step [E] (mm)
Height of Typical Step [F] (mm)
Stringer Position [H] (mm)
Total Run [G] (mm)
Stringer Length (mm)
Stair/Rail Angle (degrees)

Stringer Mount Type: [?]     Standard        Flush ## Manual Stair Calculator Metric

Input: Total Rise [A] (ex. 1525) (mm)
Total Run [G] (ex. 2430) (mm)
Number of Steps (Risers)

Stair Results:
Step Height [F] (mm)
Steps on Stringer [D]
Height of First Step [E] (mm)
Stringer Position [H] (mm)
Stringer Length (mm)
Stair/Rail Angle (degrees)

Stringer Mount Type: [?]     Standard       Flush

Some results may not meet code requirements

Try adjusting the Total Rise, the Total Run, or the Number of Steps, and re-click

Calculate Stairs ## Metric Stair Calculator Results and related Building Codes**

Stringer - The stringer is the structural part of a set of stairs. They are cut from 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. It is used to determine the length of 2x12 material required to layout a stair stringer.

Total Rise [A] - The total rise of a set of stairs is the vertical distance between the bottom of the first step and the top of the finished landing. The Total Rise should be not larger than 3835 millimeters (151 inches) between landings or floor levels.

Total Run [G] - The Total Run is the horizontal length of a stair stringer.  It is equal to the number of treads multiplied by the typical Tread Depth [B].

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 greatest step height and the smallest should not exceed 9.5 millimeters (3/8 inch). Open risers with openings more then 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 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 Tread Depth [B] should not be less than 254 millimeters (10 inches). In a given run of stairs, the greatest tread depth should not exceed the smallest by more than 9.5 millimeters (3/8 inches). Typically, a single 2x12 or two 2x6s are used for stair tread material.

Number of Steps (Risers) - The number of risers is not necessarily the same as the number of 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 Stringer Mount Type is Standard, the number of risers will be one more than the number of Steps on Stringer [D].

Stringer Position [H] - The stringer position refers to how far below the finished height of the upper landing the stringer will be attached.

Headroom - the headroom should not be less than 2032 millimeters (6 feet, 8 inches), measured vertically from the stair tread nosing to the nearest ceiling object.

Stair/Rail Angle - the angle is most useful for determining the bevel cut on a stair rail post. It can also be useful for cutting the angle on the top of the stair rail pickets.

Stringer Length - the stringer length calculation is the minimum length of 2x12 material that is required to layout and cut the stringer.

Stairs and Landings - Landings are used to break up runs of stairs. Building code states that the minimum width of a landing should not be less than the width of the flight of stairs that is 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.

** Note: Building Code information was obtained from the 2021 International Residential Code for One- and Two-Family Dwellings - Section 311 - MEANS OF EGRESS.

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