Free deck stairs calculator: risers, stringers, treads and boards
Get the risers, the riser height, the stringers and the tread and riser boards of a deck stair in seconds, free and without an account. One row per flight: its total rise, from the deck surface to the landing below, and its width. Enter the maximum riser and the tread run, or pick a code to fill the figures it prints, then your stringer spacing and boards: each flight's line shows its risers, the riser height to the 1/16 in, the treads, the total run and the stringer length.
Stairs: what the codes say (reference)
As read. Codes change by edition and by state, province or city: check the one that applies before you build.
| As read | |
|---|---|
| IRC 2021 (US) | Stairs at least 36 in wide (R311.7.1); risers at most 7 3/4 in (R311.7.5.1); treads at least 10 in (R311.7.5.2); a handrail on at least one side of a flight of four or more risers, 34 to 38 in high (R311.7.8) |
| IRC 2021, guards | Where the walking surface is more than 30 in above the grade within 36 in of its open side; at least 36 in high, 34 in on the open sides of stairs; no opening a 4 3/8 in sphere passes on stairs (R312.1) |
| NBC 2020, private stairs (Canada) | Rise 125 to 200 mm, run 255 to 355 mm (Tables 9.8.4.1 and 9.8.4.2); risers and runs uniform within 5 mm between adjacent steps and 10 mm in a flight (9.8.4.4); a guard where the drop is more than 600 mm (9.8.8.1) |
| AWC DCA 6 (US) | Stringers at least 2x12, at least three when only cut stringers are used, at most 18 in on center on stairs wider than 36 in; a landing when the stair rises more than 12 ft. Where it differs from the IRC, the IRC applies |
Sources: IRC 2021, R312.1 and R311.7; NBC 2020, 9.8; AWC DCA 6
Stringers and treads: what the makers say (reference)
As printed for their composite boards: your product's guide has the last word.
| As printed | |
|---|---|
| Fiberon | Stringers at most 12 in on center for residential stairs, 8 in for commercial; square edge boards only on treads; riser boards fastened at every stringer with two screws |
| Deckorators | Stringers at most 9 in on center (8 in for commercial use), at least 5 stringers; two fasteners per tread at each stringer |
| TimberTech | A tread at least two full boards deep; stringers at most 9 in on center for Premier, 10 in for Legacy and Reserve; steps without a riser board not recommended; no hidden fasteners on stairs |
| Trex (Canada) | Stair stringers 200 to 250 mm on center |
Sources: Fiberon, decking install guide; Deckorators, stair treads; TimberTech composite guide; Trex 2026 guide
How it is calculated
Risers = total rise / maximum riser, rounded up; riser height = total rise / risers; treads = risers - 1 (the deck is the top step). Total run = treads x tread run. Stringer length = square root of (rise² + total run²), along the slope: order the next stock length up, with the top and bottom cuts. Stringers = width / spacing, rounded up, + 1. Tread boards = treads x boards per tread x width; riser boards = risers x boards per riser x width (0 for open risers). Screws = (tread boards + riser boards) x stringers x screws per board at each stringer. A code picked fills its maximum riser and minimum tread as read; with Other picked, every figure is yours.
Example: a stair to the yard
From our template page's demo: a stair to the yard rising 36 in, 3.5 ft wide, with risers of at most 7.75 in (7 3/4 in, the IRC 2021 figure) and 11.25 in treads. Stringers every 12 in (Fiberon's residential maximum), 2 boards per tread, 1 riser board per riser and 2 screws per board at each stringer: 5 risers and 4 treads, 5 stringers, 28 ft of tread boards, 17.5 ft of riser boards and 130 screws. The flight's line gives the riser height to the 1/16 in, the total run and the stringer length.
The whole job in MesuPro
Deck survey
Surfaces and decking, joists and fasteners, hidden clips, beams and concrete, guards, stairs with stringers and risers, fascia.
You get: Deck area Board rows Decking length
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