Stair Total Run from Risers and Tread Depth
Also known as stair run · how far do stairs stick out
Worked example: 14 risers, 10 in treads → 130 in of run (3.302 m) — press Try an example to run it live, then adjust anything.
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Stair Total Run from Risers and Tread Depth explained
The count that catches people out is that a flight has one fewer tread than it has risers, because the upper floor itself serves as the last tread. Fourteen risers means thirteen treads, so at 10 in each the stair eats in of floor, just shy of 11 ft. This is the number that decides whether the stair fits the hole in the floor above, and it is worth knowing before the joists are cut.
Run backwards it becomes a planning tool. If you have 3.25 m of floor to give and want a 250 mm going, you get 13 treads and therefore 14 risers, which then fixes your riser height through the rise-and-riser formula. Note that nosing overhang does not change this arithmetic: the going is measured nosing to nosing, so an overhang adds tread surface without adding run.
Stair Total Run from Risers and Tread Depth formula
- = Total run (m)
- = Number of risers
- = Tread depth (m)
Missing one of these? Work it out first, then come back
- Total run — Stair Stringer Length, Drain Line Fall from Slope and Run
- Number of risers — Stair Riser Count from Total Rise, Pieces from a Stock Length (with Saw Kerf)
- Tread depth — Stair Comfort Rule (2R + T), Hydrostatic Pressure (P = ρgh)