Stair Calculator
Work out steps, riser height and total run for a staircase.
Vertical height from finished floor to finished floor.
Results update as you type.
How it works
A stair calculator turns the one measurement you cannot change — the total rise from one finished floor to the next — into a buildable staircase by working out how many steps it needs, how tall each riser will be, and how much horizontal room the flight will occupy. You enter the total rise plus your preferred riser height and tread depth, and the tool divides the rise by the target riser and rounds up to a whole number of steps, because you can only build complete risers. It then shares the total rise evenly across those steps to find the actual riser height, which almost always differs slightly from your target and, crucially, is the same for every step: uneven risers are a serious trip hazard and are prohibited by building codes, which typically allow only a small variation between the tallest and shortest riser in a flight. The total run tells you whether the stair will fit the space you have, using one fewer tread than steps because the final step is the upper floor itself. Comfortable stairs balance riser and tread so the climb feels natural, often checked against a rule such as two risers plus one tread landing near 25 inches. Carpenters, deck builders and remodelers use this to lay out a stringer before cutting, and homeowners use it to see whether a staircase will fit. Always confirm riser, tread and headroom limits against your local building code.
Steps = ⌈total rise ÷ target riser⌉; actual riser = total rise ÷ steps; total run = (steps − 1) × tread depth
The total rise is the fixed vertical distance the stair must climb, so dividing it by your target riser height gives roughly how many steps are needed, and rounding up ensures the risers end up a little shorter rather than taller than the target. Dividing the total rise by that whole number of steps gives the actual riser height, which is identical for every step because building codes require uniform risers. The total run uses one fewer tread than there are steps, since the top step lands on the upper floor and needs no tread of its own, multiplied by the tread depth.
Source:Standard construction estimation
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter total rise.
- 2
Adjust the options
Adjust target riser height and tread depth if they apply — sensible defaults are already set.
- 3
Read your result
Number of steps updates instantly as you type — no button to press.
Frequently asked questions
What is a comfortable stair riser height?
Most codes cap risers around 7.75 inches, and a comfortable, easy climb usually falls between 7 and 7.5 inches. Taller risers make a steeper, more tiring stair, while very short risers stretch the run and take more floor space. This calculator lets you set a target riser, then reports the actual height once the rise is divided into whole steps, so you can adjust until it feels right.
Why must all the risers be the same height?
People climb stairs by feel, expecting every step to be identical, so a single riser that is taller or shorter than the rest is a common cause of trips and falls. Building codes reflect this by allowing only a small variation, often three-eighths of an inch, between the largest and smallest riser in a flight. That is why the calculator divides the total rise evenly across all the steps rather than leaving an odd step at the top.
How is the total run different from the total rise?
The total rise is the vertical height the stair climbs, measured floor to floor, while the total run is the horizontal distance it covers from the bottom step to the top. Run depends on tread depth and the number of treads, using one fewer tread than steps because the top step is the landing. Checking the run early tells you whether the staircase will actually fit the available floor space.
What tread depth should I use?
Tread depth, the front-to-back walking surface, is commonly around 10 to 11 inches, with codes setting a minimum near 10 inches for the part you step on. Deeper treads feel safer and more comfortable but lengthen the total run and demand more floor space. Pair tread depth and riser height together so the stair is neither too steep nor too shallow, and confirm both against your local code.
Does this calculator replace local building codes?
No. It is a planning tool that gives you a sound starting layout for steps, riser height and run, but the legally binding figures come from your local building code and any inspector. Codes govern maximum riser, minimum tread, minimum headroom, handrail requirements and nosing, and they vary by jurisdiction. Use this result to design and check feasibility, then verify every dimension against the code that applies to your project.