Risers, tread positions, and floor space
The upper landing is the final stepping surface, so there is one fewer tread than risers. Floor run includes those treads. The untrimmed pitch-line length includes one triangle for each riser; it is a geometric reference, not the length of a finished cut board. Dimensions and table coordinates use your selected unit.
To estimate the boards for the surrounding deck, use the Deck Board Calculator .
For an individual right-triangle check, use the Pythagorean Theorem Calculator .
The formula
H is total finished height, g is the horizontal going between nosings, and hmax is the entered riser limit. Manual mode substitutes your whole-number riser count. The pitch line extends across N equal rise/run triangles; actual stringer ends need trimming and support details. A positive available run enables a separate floor-space comparison.
A 108-inch deck rise
For a finished rise of 108 inches, a 7.75-inch maximum riser, and 10-inch going, the tool chooses 14 risers. Each is about 7.714 inches high, with 13 treads and a 130-inch floor run. The untrimmed pitch line is about 176.816 inches. If only 120 inches of run is available, the shortfall is 10 inches.
How to use this calculator
- Select inches or millimeters and enter every dimension in that unit. Changing the unit relabels the inputs; it does not convert an existing entry.
- Enter the finished rise and going. Use the maximum-height method or select manual mode and enter 2–100 risers.
- Optionally enter available floor run, calculate, and expand the step table to review each finished height and tread position.
Measure the finished surfaces
Floor finishes change stair height. Measure between the actual lower and upper walking surfaces, rather than framing surfaces that will later receive decking or flooring. The equal-riser output describes this finished geometry. It does not subtract tread thickness from the bottom of a stringer.
Floor run and board length describe different things
For this tool, a flight with 14 risers reaches its upper landing after 13 separate treads. That floor footprint is different from a pitch line projected through 14 rise/run triangles. The longer reference line helps explain the slope, but ordering lumber requires allowances for end cuts, attachment, stock width, remaining wood below notches, and support spacing.
Read the layout before choosing a final design
The table starts at the lower finished surface and records the height at every riser. Run is measured from the first riser, with the first tread directly above that position. The fit comparison only checks your entered floor distance and riser-height limit. It does not check headroom, landings, nosing, handrails, uniformity after construction, or structural capacity. Verify those details for the location and stair system before cutting.
Assumptions & limitations
What this calculation assumes
- One straight flight with equal finished risers and constant going; the upper landing replaces the last tread.
What to keep in mind
- Geometric planning only; no structural sizing, code certification, stock selection, tread-thickness adjustments, or finished cut lengths.
- Changing dimension units does not convert the entered values.
Common questions
Why are there fewer treads than risers?
The upper landing supplies the last walking surface. A 14-riser flight has 13 separate treads under this convention.
Can I use the pitch-line length to order a board?
Use it as a geometric reference only. End cuts, attachments, stock width, notch depth, supports, and your stair design determine the actual board needed.
Does a passing planning check mean the stairs meet building code?
No. It compares only the riser limit and optional available run you entered. Local requirements and structural details need their own review.