Work out step count, riser height, run length, and stringer length from a total rise, right in your browser.
Stair Calculator Online
Work out step count, riser height, run length, and stringer length from a total rise, right in your browser.
The Stair Calculator runs entirely in your browser. The rise, riser, and tread values you enter never leave your device and nothing is uploaded to ArrayKit.
Stair Calculator turns a total floor-to-floor rise into a complete stair layout: the number of steps, the exact riser height for each one, the total horizontal run, the stringer (diagonal board) length, and the incline angle. Enter your total rise, a target riser height, and a tread depth, and it rounds to the nearest whole number of equal steps so the flight climbs evenly from bottom to top. Switch between US/imperial (inches) and metric (centimeters) units with a single toggle — the math converts internally so you can plan in whichever unit your plans or your lumber yard use. It is built for DIYers framing a deck or porch staircase, contractors roughing out stringers before a cut list, and anyone sketching a staircase who wants the geometry checked before reaching for a saw. Every calculation runs locally on your device.
Features
Computes step count from total rise and a target riser height
Rounds to a whole number of steps so every riser stays equal
Calculates total run length from tread depth and step count
Works out stringer (diagonal board) length using the Pythagorean theorem
Reports the stair incline angle in degrees
Toggle between US/imperial (inches) and metric (centimeters) units
Copy a plain-text summary of every result at once
Runs entirely in your browser — no project dimensions are uploaded
How to use the Stair Calculator
Choose US/imperial or metric units
Enter the total floor-to-floor rise
Set your target riser height and tread depth
Read the step count, riser, run, stringer length, and angle
Example
Input
total rise 108 in
Output
14 steps · riser 7.71 in
108 in ÷ 7.5 in target riser rounds to 14 equal steps at 7.71 in each.
Common errors & troubleshooting
Step count looks too low or too high for the space. — Adjust the target riser height — a lower target (closer to 7 in / 18 cm) yields more, gentler steps; a higher target yields fewer, steeper steps. Most codes cap riser height around 7.75 in (19.7 cm).
Stringer length seems short for how far the stairs actually run. — Remember run length is treads × tread depth, and the top step lands on the upper floor, so the tread count is one less than the step count. Increase the tread depth if your landing needs more horizontal space.
Riser height calculated as 7.71 in instead of the entered 7.5 in target. — That is expected — the calculator rounds the step count to a whole number first, then divides the total rise evenly across those steps, so the actual riser is close to, not exactly, your target.
Mixing inches and centimeters gives an unrealistic result. — Switch the unit toggle before entering values — all three inputs (total rise, target riser, tread) are read in the currently selected unit.
Frequently asked questions
What does the Stair Calculator actually solve for?
It takes your total rise (the vertical floor-to-floor height), a target riser height, and a tread depth, then returns the number of steps, the exact riser height, the total run, the stringer length, and the incline angle.
How does the stair rise and run calculator round the step count?
It divides the total rise by your target riser height and rounds to the nearest whole number of steps, then recalculates the riser height so every step in the flight is exactly equal.
How is stringer length calculated?
The Stair Calculator applies the Pythagorean theorem to the total rise and total run: stringer length = the square root of (rise squared + run squared), which is the length of board needed to cut the stringer.
Can the number of stairs calculator work in metric units?
Yes. Toggle to metric and enter total rise, riser, and tread in centimeters — the underlying math converts internally so the results stay accurate in either unit system.
Does the stair calculator check local building code?
No. It computes the geometry only; riser height, tread depth, headroom, and handrail rules vary by jurisdiction, so always verify against your local building code before cutting material.
Is any of my staircase data uploaded?
No. The Stair Calculator runs entirely in your browser — the rise, riser, and tread values you enter never leave your device.
Related tools
Square Footage Calculator — Calculate area in square feet or meters for rooms and projects, with cost.
Roofing Calculator — Estimate roof area, squares and shingle bundles from footprint and pitch.
Concrete Calculator — Estimate concrete volume and bags for slabs, footings and columns.