How many steps for a 9 ft rise?

108 in ÷ 7.75 in = 13.9, so 14 risers of 7.71 in and 13 treads. At a 10.5 in run the stair runs 136.5 in, about 11.4 ft, and the stringer is about 14.5 ft.

What is the code for stairs?

The International Residential Code allows risers up to 7¾ in and treads at least 10 in, with no more than ⅜ in variation between risers, a width of at least 36 in, and 6 ft 8 in of headroom. Local codes can differ; check yours.

How long a board for a stringer?

The stringer length plus a little for the cuts. A 14 ft stringer needs a 16 ft 2×12; the sheet counts 12 ft boards, so use the length line to pick the board.

Stair calculator

Form 96 · Materials estimateFigures checked 2026-09-04

US customary

Measurements

Total rise(in)Finished floor to finished floor

Stair width(in)IRC minimum 36 in

What you need

Quantity · Amount

01Risers108 in ÷ 7.75 in max, rounded up14
02Riser height, eachwithin the IRC limits7.71 in
03Treadsone fewer than risers13
04Total run13 × 10.5 in137 in
05Stringer length√(rise² + run²)174 in
06Stringers36 in wide at 16 in; 2 × 12 ft board each4$256
07Tread boards$14 per tread13$182

Total, lumber$438

Riser plus tread should land between 17 and 18 inches for a comfortable stair.
Deduct the tread thickness from the bottom of the stringer so every rise is equal.

The material

Max riser height(in)IRC residential max 7¾ in; 7–7½ is comfortable

Tread run(in)IRC minimum 10 in; 10½–11 is comfortable

Stringer spacing(in)16 in for 5/4 deck boards; 12 for composite

Prices — put in what you were quoted

2×12 stringer board($ per each)Per 2×12×12 ft PT board; longer stairs need longer boards

Tread board($ per each)Per 2×12 tread or two 5/4×6 boards, per step

Total, lumber14 risers at 7.71 in$438

Where these figures come from

IRC R311.7: riser max 7¾ in, tread min 10 in, width min 36 in (2021 edition; local amendments apply).
Prices are typical US lumber-yard figures at the date on this sheet.

Measure the total rise from the lower finished floor to the upper finished floor. The sheet divides it into equal risers no taller than the limit you set (the IRC residential maximum is 7¾ in), gives the tread count, the total run, the stringer length by Pythagoras, and counts stringers, tread boards and riser boards for a deck or basement stair.

Worked examples

Basement stair, 108 in rise: 14 — risers, about $438 in lumber.
Deck steps, 36 in rise, 48 in wide: 5 — risers, about $184 in lumber.

How it is worked out

Risers = total rise ÷ maximum riser, rounded up. Riser height = total rise ÷ risers. Treads = risers − 1. Total run = treads × tread run. Stringer = √(rise² + run²). Stringers = width ÷ spacing, rounded up, plus one.

The figures behind it

IRC R311.7: riser max 7¾ in, tread min 10 in, width min 36 in (2021 edition; local amendments apply).
Prices are typical US lumber-yard figures at the date on this sheet.

Every figure here is an estimate. Materials vary with moisture, compaction and product; order a little extra and confirm quantities with your supplier.

Questions people ask

How many steps for a 9 ft rise?: 108 in ÷ 7.75 in = 13.9, so 14 risers of 7.71 in and 13 treads. At a 10.5 in run the stair runs 136.5 in, about 11.4 ft, and the stringer is about 14.5 ft.
What is the code for stairs?: The International Residential Code allows risers up to 7¾ in and treads at least 10 in, with no more than ⅜ in variation between risers, a width of at least 36 in, and 6 ft 8 in of headroom. Local codes can differ; check yours.
How long a board for a stringer?: The stringer length plus a little for the cuts. A 14 ft stringer needs a 16 ft 2×12; the sheet counts 12 ft boards, so use the length line to pick the board.

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