Inputs
Results
All values update instantly. Effective going = tread depth − nosing. Angles per flight.
| Metric | Value |
|---|
Example Data
Sample scenarios to sanity‑check your own inputs.
| Name | Units | Rise | Pref Riser | Tread | Nosing | Landing | Width | Shape | Waste % |
|---|---|---|---|---|---|---|---|---|---|
| Domestic L‑shape baseline | mm | 2700 | 175 | 260 | 25 | 900 | 1000 | L | 7 |
| Compact U‑shape townhouse | mm | 2850 | 180 | 250 | 20 | 1000 | 900 | U | 8 |
| Imperial L‑shape demo | in | 112 | 7 | 10.25 | 1 | 36 | 39 | L | 6 |
Formula used
- N = round(R_total / R_pref) → total risers; actual riser h = R_total / N.
- Auto‑split: r1 = round(N/2) unless custom. Then r2 = N − r1.
- Per flight treads: t1 = r1, t2 = r2 − 1; total treads t = N − 1.
- Effective going: g_eff = tread − nosing (min 0).
- Runs: run1 = t1 · g_eff, run2 = t2 · g_eff.
- Rises: rise1 = r1 · h, rise2 = r2 · h.
- Angles: θ1 = atan(rise1/run1), θ2 = atan(rise2/run2) (degrees).
- Stringers: L1 = √(run1² + rise1²), L2 = √(run2² + rise2²).
- Areas (for carpet): A_treads = width · tread · t, A_nose = width · nosing · t, A_risers = width · h · N, A_landing = width · landing.
- Total area with waste: A_total = (A_treads + A_nose + A_risers + A_landing) · (1 + waste%).
Formulas assume standard rectangular treads with one turning landing. Always verify against local code and site dimensions.
How to use this calculator
- Select your preferred unit system and enter the floor‑to‑floor height.
- Enter a target riser height and tread depth. Add nosing projection if applicable.
- Specify landing length and stair width. Choose L‑shape or U‑shape.
- Optionally set the number of risers in the first flight to bias the split.
- Click Calculate. Review riser count, per‑flight runs and angles, stringer lengths, and carpet areas.
- Use Download CSV for spreadsheets, or Download PDF to share a summary with teams on site.
FAQs
It rounds the total rise divided by your preferred riser to the nearest whole number of risers. The exact riser height is then the total rise divided by that count.
Stair run is measured nosing‑to‑nosing horizontally. If a nosing projects, the horizontal going reduces by that projection, so effective going is tread depth minus nosing.
Yes. Enter a custom number of risers for the first flight. The calculator will allocate the remainder to the second flight automatically.
No. It provides geometry and carpet coverage estimates. Always check local code for permitted riser and going ranges and minimum landing sizes.
The model adds an allowance equal to stair width times nosing projection per tread to approximate the wrap. Adjust your waste factor to be conservative.
Both L and U shapes use one landing in this model. The carpet area changes mainly with riser count, going, landing length, and stair width rather than the turn angle.
At‑a‑glance
- Two flights with a single landing (L or U).
- Auto or custom split of risers between flights.
- Per‑flight runs, rises, pitch angles, and stringer lengths.
- Total treads, effective going, overall run estimate.
- Carpet coverage including risers, treads, nosing wrap, and landing with waste factor.