The full dimension checklist
| Dimension | What it is | Typical range (US, IRC-style) | Typical range (UK, Part K-style) |
|---|---|---|---|
| Riser height | Vertical height of one step | About 4-7.75in | About 150-220mm |
| Tread depth (going) | Horizontal depth of one tread | About 10in minimum | About 220mm minimum |
| Total rise | Full floor-to-floor height | Site-specific | Site-specific |
| Total run | Horizontal flight footprint | Site-specific | Site-specific |
| Stair width | Clear width between walls/rails | About 36in minimum typical | About 800-900mm typical |
| Headroom | Vertical clearance above pitch line | About 6ft 8in minimum | About 2.0m minimum |
| Nosing | Tread overhang past riser face | About 0.75-1.25in typical | About 16-25mm typical |
| Handrail height | Height above tread nosing | About 34-38in | About 900-1000mm |
All figures above are widely cited defaults for common residential codes and vary by jurisdiction, edition, and occupancy type — always confirm the specific adopted code with your local building authority before finalising a design.
How the dimensions interact
None of these numbers exist in isolation. Riser height and tread depth together set the comfort of the climb (see Blondel's rule). Total rise and total run together set the stringer's pitch angle, which in turn affects headroom clearance at every point along the flight. Stair width interacts with stringer count and handrail placement. A dimensions calculator's value is checking all of these together rather than one at a time, since a change to one number often shifts what's acceptable for another.
Worked example: full dimension set for one flight
Total rise 105in, 14 risers, 36in width, straight flight, no turn.
| Dimension | Calculated value | Passes typical IRC? |
|---|---|---|
| Riser height | 105 / 14 = 7.5in | Yes (under 7.75in) |
| Tread depth (chosen) | 10.5in | Yes (over 10in) |
| Total run | 13 × 10.5in = 136.5in | n/a, footprint check |
| Stair width | 36in | Yes (meets 36in typical min) |
| Headroom (assume 8ft ceiling above) | Approx 6ft 9in at tightest point | Yes (over 6ft 8in), verify locally |
| Nosing | 1in | Within typical range |
Width: the dimension people forget to check
Stair width is measured as the clear distance between finished wall surfaces or between handrails if both sides have one, not the rough framing opening. A common mistake is measuring the framed stairwell width and forgetting that drywall, trim and a handrail projection can together remove 3-5in of usable clear width, potentially dropping a stair below the code minimum after finishing.
Measure clear width after finishes, not framing
Drywall, trim, and handrail projection into the stairwell can reduce clear width by several inches compared to the rough framed opening. Always check width against the finished dimensions, not the studs.
Nosing and how it's counted
Nosing is the projection of the tread past the riser face below it. It counts toward the minimum tread depth in some codes (measured tread depth includes the nosing projection up to a limit) but not in others, which is a common source of confusion when a tread appears to pass on paper but the code inspector measures it differently. Check whether your jurisdiction's tread depth minimum is measured with or without nosing before relying on a borderline pass.
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Open the stair runner calculatorHandrail height and dimension interplay
Handrail height is measured vertically from the nosing of each tread, not from the floor, which means it must be re-checked at every point along a flight with varying pitch (such as through a winder turn) since the vertical distance from a sloped rail to the nosing below it changes if the pitch changes.
Using a full dimension check before you build
Run every dimension through a single check before finalising drawings: riser and tread for comfort and code, total run for footprint, width for accessibility and code minimum, headroom for clearance, nosing for tread-depth counting rules, and handrail height for accessibility. Catching one dimension out of range at the drawing stage is far cheaper than catching it after stringers are cut.
Whatever you decide, get the numbers first: the stair runner calculator doubles as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length the first time.
Frequently asked questions
What dimensions does a full stair check need?
Riser height, tread depth, total rise, total run, stair width, headroom, nosing, and handrail height, each checked against the relevant code minimum or maximum.
Is nosing counted as part of tread depth?
It depends on the code — some measure tread depth including a portion of the nosing projection, others exclude it. Check your specific jurisdiction's measuring method before relying on a borderline pass.
How is stair width measured?
As the clear distance between finished wall surfaces or handrails, after drywall, trim and any handrail projection — not the rough framed stairwell opening, which is usually a few inches wider.
What's a typical minimum stair width?
Around 36in is a commonly cited residential minimum in the US, and roughly 800-900mm is typical guidance in the UK, though exact minimums depend on the specific code, occupancy and any means-of-egress requirements.
How is handrail height measured?
Vertically from the nosing of the tread directly below the rail, not from the floor — this needs re-checking through any section where the pitch changes, such as a winder turn.
What headroom clearance do I need?
Commonly cited minimums are about 6ft 8in (IRC) or 2.0m (UK Part K), measured from the pitch line (the line touching each tread's nosing) up to the ceiling or any obstruction above.
Why check all dimensions together rather than one at a time?
Because they interact — riser and tread affect pitch angle, pitch angle affects headroom, width affects stringer count and handrail placement. Changing one can push another out of range.
Where do these code figures come from?
They're widely cited defaults based on common codes like the IRC and UK Part K, but exact figures vary by jurisdiction and edition — always verify with your local building department.
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Open the stair calculatorEvery guide is written from hands-on measuring and fitting experience, checked against the calculator’s own maths, and re-reviewed whenever prices or methods change. Read our editorial standards.