Figure

Roof and stairs

Stair layout

Use total rise, total run, and step targets to calculate a stair layout and its related results.1

Stair layout relates total rise, horizontal run and target step dimensions. Calculated riser and tread sizes can differ from those targets. The examples state the rounding, headroom and floor-thickness assumptions that affect later results.

Total rise is the vertical floor-to-floor height. Total run is the horizontal distance available for the flight. A target riser or tread is a starting preference; the calculator chooses a whole-number layout and reports the resulting dimensions.

Read the actual riser, tread, count and headroom results together, using the floor-thickness and rounding settings shown in the example. These are geometric worked examples; they do not establish that a stair design meets the requirements for a particular project.

Only floor-to-floor rise known

Use floor-to-floor rise and your desired riser. Check Tread, Headroom and Floor in the setup. Type a value with units and tap its key to change it.

Settings for this example

Stair tread width
10 INCH
Stair headroom
6 FEET 8 INCH
Floor thickness
10 INCH

Start a new calculation

Use 2nd if a unit is above its button.

  1. Start fresh

    Press Clear entry, then Clear entry.

  2. Press the keys

    Press Select length units.

Open Stairs

Skip if Stairs is already open. Skip Close if no mode is open.

  1. Press Close calculation mode, then Open Stairs.

Enter and calculate

  1. Desired riser

    Press 7, then inches, then 1, then Fraction, then 2, then Store target riser.

  2. Floor-to-floor rise

    Press 9, then feet, then 11, then inches, then Store rise.

  3. Complete the value

    Press Equals.

Results in orderPress = to continue

  1. Riser height7 and 7/16 inches
  2. Number of risers16
  3. Tread depth10 inches
  4. Number of treads15
  5. Run needed12 feet 6 inches
  6. Stringer length15 feet 6 and 15/16 inches
  7. Incline36.64003°
  8. Stairwell opening10 feet 1 inch
  9. Riser height again7 and 7/16 inches

Keep in mind

There is one fewer tread than risers. Step dimensions are rounded to the selected fraction precision before the opening, stringer and incline calculations. Headroom and floor thickness affect the opening.

Only total run known

Use total horizontal run and your desired riser. Check Tread, Headroom and Floor in the setup. Type a value with units and tap its key to change it.

Settings for this example

Stair tread width
10 INCH
Stair headroom
6 FEET 8 INCH
Floor thickness
10 INCH

Start a new calculation

Use 2nd if a unit is above its button.

  1. Start fresh

    Press Clear entry, then Clear entry.

  2. Press the keys

    Press Select length units.

Open Stairs

Skip if Stairs is already open. Skip Close if no mode is open.

  1. Press Close calculation mode, then Open Stairs.

Enter and calculate

  1. Desired riser

    Press 7, then inches, then 1, then Fraction, then 2, then Store target riser.

  2. Total run

    Press 20, then feet, then Store run.

  3. Complete the value

    Press Equals.

Results in orderPress = to continue

  1. Riser height7 and 1/2 inches
  2. Number of risers25
  3. Tread depth10 inches
  4. Number of treads24
  5. Total rise15 feet 7 and 1/2 inches
  6. Stringer length25 feet 0 inches
  7. Incline36.8699°
  8. Stairwell opening10 feet 0 inches
  9. Riser height again7 and 1/2 inches

Keep in mind

The total run determines tread count. The desired riser supplies the calculated rise; it is not an entered floor-to-floor measurement. Step dimensions are rounded to Fraction precision before opening, stringer and incline are calculated.

Both rise and run known

Use floor-to-floor rise, total horizontal run and desired riser. Check Headroom and Floor in the setup. Change either with its key.

Settings for this example

Stair tread width
10 INCH
Stair headroom
6 FEET 8 INCH
Floor thickness
10 INCH

Start a new calculation

Use 2nd if a unit is above its button.

  1. Start fresh

    Press Clear entry, then Clear entry.

  2. Press the keys

    Press Select length units.

Open Stairs

Skip if Stairs is already open. Skip Close if no mode is open.

  1. Press Close calculation mode, then Open Stairs.

Enter and calculate

  1. Desired riser

    Press 7, then inches, then 1, then Fraction, then 2, then Store target riser.

  2. Floor-to-floor rise

    Press 10, then feet, then 1, then inches, then Store rise.

  3. Total run

    Press 15, then feet, then 5, then inches, then Store run.

  4. Complete the value

    Press Equals.

Results in orderPress = to continue

  1. Riser height7 and 9/16 inches
  2. Number of risers16
  3. Tread depth12 and 5/16 inches
  4. Number of treads15
  5. Stringer length18 feet 0 and 3/4 inches
  6. Incline31.5588°
  7. Stairwell opening12 feet 2 and 1/2 inches
  8. Riser height again7 and 9/16 inches

Keep in mind

The app flags a riser above the desired height. That caution compares calculator targets; it is not a building-code assessment. Rounding differences appear beside Riser height or Tread depth. Tread depth excludes nosing. Step dimensions are rounded to Fraction precision before opening, stringer and incline are calculated.

Set up the stair calculation

Enter values with units, then tap Riser, Tread, Headroom or Floor. These edits belong to this stair setup.

Start a new calculation

Use 2nd if a unit is above its button.

  1. Start fresh

    Press Clear entry, then Clear entry.

  2. Press the keys

    Press Select length units.

Open Stairs

Skip if Stairs is already open. Skip Close if no mode is open.

  1. Press Close calculation mode, then Open Stairs.

Set the target riser

  1. Desired riser

    Press 8, then inches, then Store target riser.
  1. Example result8 inches

Set the other dimensions

Enter each value with units, then tap its key.

  1. Tread target

    Include units

    Press 11, then inches, then Store target tread.

  2. Headroom

    Include units

    Press 6, then feet, then 10, then inches, then Store headroom.

  3. Floor thickness

    Include units

    Press 12, then inches, then Store floor thickness.
  1. Example result12 inches

Keep in mind

Type each dimension with units, then tap Riser, Tread, Headroom or Floor. Riser and Tread are targets; calculated step sizes may differ. Next, enter Rise or Run with units, tap its key and press =. One C keeps the setup; two consecutive C restores saved defaults.

Display assumptions

  1. Fraction precision: 1/16″; Fraction format: Simplified; Angle decimal places: Variable. ↩

Keep the guide beside your calculation.

These examples are built into Figure. Open Help while you calculate, then return to the same guide and reading position.

See Help in Figure →