Calculate equal stair risers, treads, horizontal run, angle, stringer length, and traditional stair proportions from floor-to-floor rise for preliminary geometry planning.
The calculator rounds the total rise divided by your user-entered riser-height design limit upward to a whole riser count, then divides the rise evenly so every calculated riser is equal.
In this calculator's single-flight model, tread count is one fewer than riser count because the upper finished floor serves as the final walking surface.
ceiling(total rise ÷ user-entered riser-height limit)total rise ÷ riser countriser count − 1tread count × horizontal going per treadatan(total rise ÷ total run), in degrees√(total rise² + total run²)2 × actual riser + tread goingFor 108 in total rise, a 7.5 in user-entered riser-height limit produces 15 risers. Each riser is 7.2 in; 14 treads at 10 in create 140 in of run, an angle of about 37.65°, and a stringer length of about 176.82 in.
For 2.8 m total rise, a 0.19 m riser-height limit, and 0.28 m tread going, the result is 15 risers at about 0.186667 m, 14 treads, 3.92 m total run, a 35.54° angle, and a 4.82 m theoretical stringer length.
With 108 in total rise, a 7.5 in riser-height limit, and 126 in available run, 15 risers create 14 equal treads at 9 in going, a 40.60° angle, and a 165.95 in theoretical stringer length.
Measure vertically between finished floor levels, accounting for final floor finishes.
Enter horizontal travel per tread. Do not substitute the tread board depth or nosing projection.
Treat the initial values as editable starting points and choose project dimensions from requirements applicable to the jurisdiction, building type, and stair system.
Rounding the riser count upward keeps actual riser height at or below the user-entered design limit. The calculator performs geometry only; acceptable finished-riser tolerances and dimensions must be verified for the project.
When horizontal space is fixed, the calculator divides available run by tread count. This reports resulting going and angle; it does not declare that geometry acceptable.
Angle uses the shared rise/run angle helper. Stringer length is the right-triangle hypotenuse between total rise and run; actual cut length, bearing, overhangs, and connections require project-specific layout.
Twice the actual riser plus tread going is a traditional proportion reference. The displayed value is informational and is not evaluated against a universal acceptable range.
Requirements differ by country, jurisdiction, occupancy, building type, route function, and whether work is new or existing. For example, the U.S. Access Board stairway guidance applies to stairs within the scope of the ADA Standards, not every stair project. This calculator does not estimate headroom, landings, guards, handrails, structural capacity, openings, or code approval.
Divide total rise by your user-entered riser-height design limit and round upward.
Divide total rise evenly by the whole-number riser count.
In this calculator's between-floors model, the upper floor serves as the final walking surface.
Multiply tread count by horizontal going per tread.
The calculator takes the arctangent of total rise divided by total run.
It is the hypotenuse of the total-rise and total-run right triangle.
It is a traditional relationship using twice riser height plus tread going, shown without a compliance judgment.
Going is the horizontal distance traveled from one step to the next, distinct from nosing projection.
Yes. Available-run mode calculates the resulting equal tread going for the available horizontal distance.
No. Verify every dimension and detail with applicable local requirements and qualified professionals.
Yes. Metric input supports millimeters, centimeters, and meters through the shared conversion system.
No. Headroom requires additional floor, ceiling, opening, and layout geometry.