How to use this calculator
- Enter Total rise in in.
- Enter Max riser in in.
- Enter Tread run in in.
- Press Calculate. The highlighted row is your order quantity; the note beneath it translates the number into real-world terms.
Formula & constants
Risers = total rise ÷ 7.75 (max code riser), rounded up; actual rise = total ÷ count. Tread run ≥ 10 in. Stringer length = √(rise² + run²). Comfort rule: 2×rise + run = 24–25 in. Every default in the fields above is editable — when your supplier’s spec sheet lists a different density, coverage rate or price, enter that number instead. The waste and compaction allowances follow common trade practice; see our methodology page for the derivation of each formula and the standards it references.
Where this fits in the project
Framing quantities chain together: footings support posts, joists set the deck frame, and surface boards follow. Price hardwood and specialty stock in board feet, sheet goods by the sheet.
How this connects to your project
No quantity stands alone — each material in the chain depends on the ones around it. These are the planning steps that pair with the stair calculator:
- Deck Calculator — Decks typically include stairs for access.
- Lumber Calculator — Stair stringers are cut from dimensional lumber.
- Joist Calculator — Stairs span between floor joist levels.
- Board Foot Calculator — Hardwood stair treads priced per board foot.
- Deck Cost Calculator — Stairs add to total deck project cost.
- Concrete Calculator — Bottom stair landing may be a concrete pad.
Frequently asked questions
What is code max for stair rise?
7-3/4 in max riser, 10 in min tread in the IRC — and riser heights within a flight can’t vary more than 3/8 in.
How many stringers per stair?
Three minimum for 36 in wide stairs with 2x treads; composite treads often demand four.
Last verified: — prices reflect current national averages. See our methodology.
Estimates are for planning. Material densities, coverage rates and prices vary by region and supplier — confirm final quantities before ordering, and check local code where structural or electrical work is involved.