Stair Rise and Run Calculator (OSHA Check)
Enter the total rise you have to climb, how many risers you are laying out and the tread depth you intend to cut. This calculator returns the riser height, the total run and the angle, and checks all of it against the stairway requirements OSHA publishes for workplaces. It verifies your layout; it never prescribes one.
Riser height
—
Results are estimates for planning purposes and do not replace a competent person's evaluation or an engineer's design. Follow the OSHA standards that apply to your work and your employer's written program.
What OSHA actually requires, paragraph by paragraph
| Requirement | General industry — 1910.25 | Construction — 1926.1052 |
|---|---|---|
| Angle from horizontal | 30 to 50 degrees — (c)(1) | 30 to 50 degrees — (a)(2) |
| Maximum riser height | 9.5 in — (c)(2) | not specified; uniformity governs |
| Minimum tread depth | 9.5 in — (c)(3) | not specified; uniformity governs |
| Uniformity | uniform riser heights and tread depths between landings — (b)(3) | uniform within each flight; variation not over 1/4 in anywhere in the system — (a)(3) |
| Minimum width | 22 in between vertical barriers — (c)(4) | landings at least 22 in wide — (a)(1) |
| Vertical clearance | 6 ft 8 in above any tread — (b)(2) | — |
| Landings | at least the stair width and 30 in deep — (b)(4) | 30 in deep, 22 in wide, every 12 ft of vertical rise — (a)(1) |
| Handrail trigger | per § 1910.28 — (b)(1) | 4 or more risers, or more than 30 in of rise, whichever is less — (c)(1) |
| Load | 5 × the anticipated live load, never under a 1,000 lb point load — (b)(6) | — |
Verified against the current text of both sections in the eCFR. The 1910.25(c)(2) and (c)(3) dimensions do not apply to standard stairs installed before January 17, 2017: OSHA deems those compliant if they meet Table D-1 or achieve the angle in (c)(1). Spiral, ship and alternating tread-type stairs have separate rules in (d), (e) and (f), and 1910.25(b)(8) allows them only where standard stairs are not feasible.
This page checks a workplace stair. It does not set your building code.
OSHA rules apply to stairs at a workplace. The stairs in a house, an apartment or a store are governed by the building code your jurisdiction has adopted, and those numbers are not the same as the OSHA numbers — they are generally tighter on riser height and looser on nothing. That code text is copyrighted and is not reproduced here.
- Get the dimensions from your building department before you cut a stringer. They will tell you which code edition is in force and what amendments your state or city has made to it.
- Measure finished floor to finished floor. Adding 3/4 in of hardwood at the top after the stringers are cut makes the top riser 3/4 in shorter than every other one — a defect on any stair, and a violation on a workplace one.
- Cut the bottom riser short by the tread thickness. When the stringer sits on the slab and the treads are applied on top, the bottom riser comes out one tread thickness taller unless you drop the stringer. This is the classic uniformity failure.
- Temporary stairs count. 1926.1052 applies to the stairs your crew uses during construction, pan stairs included — and 1926.1052(b) prohibits foot traffic on unfilled pan stairs unless they are temporarily fitted to the top edge of each pan.
How it's calculated
- Riser height
riser height = total rise / number of risersEvery riser in a flight is the same height by definition of the layout, and OSHA requires it to be so in fact: 1910.25(b)(3) requires uniform riser heights and tread depths between landings, and 1926.1052(a)(3) limits variation to 1/4 in in any stairway system.- Number of treads
treads = risers − 1The top riser lands on the upper floor, which is not a tread. This is the single most common arithmetic error in a stair layout.- Total run
total run = treads × tread depth- Stair angle
angle = arctan( riser height / tread depth )OSHA requires standard stairs to be installed at 30 to 50 degrees from the horizontal in general industry, 1910.25(c)(1), and between 30 and 50 degrees in construction, 1926.1052(a)(2).- Stringer length
stringer length = square root( total rise² + total run² )The straight-line length along the slope, from the bottom of the first riser to the top of the last tread. Add for the plumb cut, the bearing at the top and any material you cut off — this is a layout dimension, not a cut list.- Handrail trigger
handrail required when risers ≥ 4 or total rise > 30 in (construction)29 CFR 1926.1052(c)(1): stairways with four or more risers, or rising more than 30 in, whichever is less, need at least one handrail and a stairrail system along each unprotected side or edge.
Frequently asked questions
Divide the total rise by the number of risers to get the riser height. Subtract one from the riser count to get the number of treads, then multiply by the tread depth for the total run. For a 108 in rise with 15 risers and 11 in treads: 7.2 in per riser, 14 treads, 154 in of run, and a 33.2 degree stair.
Because the last riser brings you up to the floor above, and that floor is not a tread. Fifteen risers make fourteen treads. Laying out fifteen treads is how a stair ends up one full step too long.
For general industry standard stairs, 29 CFR 1910.25(c) sets a maximum riser height of 9.5 in, a minimum tread depth of 9.5 in, a minimum width of 22 in, and an angle between 30 and 50 degrees. Paragraph (b)(3) requires uniform riser heights and tread depths between landings. Construction stairways under 1926.1052(a) use the same 30 to 50 degree range and cap riser and tread variation at 1/4 in.
In construction, not more than 1/4 in anywhere in the stairway system — 1926.1052(a)(3), which explicitly includes any foundation structure used as one of the treads. General industry requires uniformity between landings without publishing a tolerance. The reason is the same in both cases: people climb stairs on autopilot, and one odd riser is a trip.
On construction stairways, at four or more risers or more than 30 in of rise, whichever comes first — 1926.1052(c)(1) — with at least one handrail plus a stairrail system along each unprotected side or edge. Handrails installed after March 15, 1991 sit at least 36 in above the tread surface.
It falls inside the OSHA limits for a workplace stair, and this calculator will tell you so. Whether it is right for your project is a building code question: residential and commercial stair dimensions come from the code your jurisdiction has adopted, and they are not the same numbers as the OSHA workplace rules. Check with your building department before you cut a stringer.
No. Spiral, ship and alternating tread-type stairs have their own dimensional rules in 1910.25(d), (e) and (f), and 1910.25(b)(8) allows them only where the employer can demonstrate that standard stairs are not feasible. This tool checks straight flights of standard stairs.
Sources & references
- 29 CFR 1910.25 — Stairways (general industry): (b)(3) uniform riser heights and tread depths between landings; (c)(1) standard stairs installed at 30 to 50 degrees; (c)(2) maximum riser height 9.5 in; (c)(3) minimum tread depth 9.5 in; (c)(4) minimum width 22 in between vertical barriers; (b)(2) vertical clearance 6 ft 8 in — Text verified against the eCFR at the 2026 snapshot. The (c)(2) and (c)(3) dimensions do not apply to standard stairs installed before January 17, 2017.
- 29 CFR 1926.1052 — Stairways (construction): (a)(2) stairs installed between 30 and 50 degrees from horizontal; (a)(3) riser height and tread depth uniform within each flight, variation not over 1/4 in in any stairway system; (a)(1) landings at least 30 in deep and 22 in wide every 12 ft of vertical rise; (c)(1) handrail and stairrail system at four or more risers or more than 30 in of rise
- Electronic Code of Federal Regulations, Title 29 — the authoritative current text of both sections
Content checked against these sources — last reviewed September 19, 2026.