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Stair Calculator

Calculate the number of risers and treads, actual step dimensions, total run, stair angle, stringer length, tread and riser material area, landing allowance, and optional project cost in metric or imperial units.

Stair Dimensions

Enter the floor-to-floor rise and preferred step dimensions.

Enter floor-to-floor rise in millimetres.
Enter your preferred riser height in millimetres.
Enter horizontal going per tread in millimetres.
Enter clear stair width in millimetres.
Optional tread projection beyond the riser face.
Used for total stringer-length estimation.
Optional space check in millimetres.
Used only when the landing configuration is selected.
Applied to tread, riser, landing, and stringer estimates.
Optional finish-material cost per square metre.

Your stair layout will appear here

Enter the total rise and preferred step dimensions, then select “Calculate Stairs.”

Calculated stair layout
—
Based on the entered total rise and target riser height
Actual riser height —
Actual tread depth —
Total horizontal run —
Stair angle —
Stringer length
—
Total stringer material
—
Tread surface area
—
Riser surface area
—
Landing area
—
Finish area with waste
—
Available-run check

Enter an available run to compare it with the calculated stair length.

Estimated finish-material cost —
This calculator is for preliminary planning only. Final stair geometry, headroom, width, landings, guards, handrails, nosings, structural support, fire safety, and accessibility must comply with the approved drawings and local building regulations.

What Does the Stair Calculator Estimate?

The calculator divides the total floor-to-floor rise by a target riser height, rounds to a practical whole number of risers, and recalculates an equal actual riser height. It then determines treads, total run, angle, and stringer length.

Included results

  • Number of risers and treads
  • Equal actual riser height
  • Horizontal tread depth and total run
  • Stair pitch angle
  • Single and total stringer length
  • Tread, riser, and landing surface area
  • Waste-adjusted finish area and optional cost

How Are Risers and Treads Related?

A straight stair commonly has one fewer tread than risers when the upper floor acts as the final tread. When the upper floor is not used as the final tread, the number of physical treads can equal the number of risers.

Important measurements

  • Total rise: Finished lower-floor level to finished upper-floor level
  • Riser: Vertical height between consecutive tread surfaces
  • Tread or going: Horizontal distance between consecutive riser faces
  • Total run: Combined horizontal distance of all tread goings
  • Stringer: Sloping structural member supporting the stair

How to Use the Stair Calculator

1

Select the measurement system

Choose metric or imperial units. The calculator updates the input labels and default values automatically.

2

Measure the total rise

Measure vertically from the finished lower-floor level to the finished upper-floor level.

3

Enter a target riser and tread depth

Use dimensions permitted by your project drawings and local building requirements.

4

Add width, landing, and space constraints

Enter stair width, optional landing depth, and available horizontal run to check whether the layout fits.

5

Review geometry and materials

Check the riser count, tread count, angle, run, stringer length, finish area, and optional cost.

Stair Planning Terms

Term Meaning Used by this calculator
Total rise Vertical floor-to-floor height Determines the required number of equal risers
Riser height Vertical height of each step Total rise divided by the calculated riser count
Tread depth Horizontal going of each step Multiplied by the number of treads to obtain total run
Nosing Projection of the tread beyond the riser face Included in tread finish-area estimation
Stringer length Sloping length supporting the flight Calculated using the total rise and horizontal run
Stair angle Pitch of the stair relative to horizontal Calculated from rise divided by run

Stair Calculation Formulas

Number of risers

Estimated risers equal total rise ÷ target riser height, rounded to the nearest whole number.

Actual riser height

Actual riser height equals total rise ÷ number of risers.

Total horizontal run

Total run equals number of treads × tread depth, plus landing depth when selected.

Stair angle and stringer length

Stair angle equals arctangent(total rise ÷ flight run). Stringer length equals √(total rise² + flight run²).

Frequently Asked Questions

Divide the total floor-to-floor rise by your target riser height, then use a whole number of equal risers. The calculator performs this adjustment and reports the resulting actual riser height.

When the upper floor acts as the final walking surface, the flight typically has one fewer physical tread than vertical risers. You can disable that option when the stair requires a separate final tread.

The calculator determines the flight angle from the stair rise and tread run only. Landing depth increases the total horizontal footprint but does not change the pitch of the stair flight.

It is the clear horizontal space available for the stair and any selected landing. Entering this value lets the calculator compare the required footprint with the available space.

No. Stair regulations vary by location, building type, occupancy, use, and accessibility requirements. Confirm the permitted rise, going, angle, headroom, width, landing, guard, and handrail dimensions locally.

It is the straight sloping flight length for estimating. Actual stringer stock and cutting layout may require extra material for bearing, connections, trimming, notches, fabrication, and structural detailing.